I have to state right upfront: the underlying question is not about how much shop charges for service, competition will take care of this; rather I am looking for a confirmation that work I am about to undertake does not have any hidden gatcha's

I acquired my jag in September, via BAT. So far it been good to me, just some routine stuff: spark plugs/coils; getting ball joint dust caps fixed for spring. various fluids changed. Thanks to @Bagpipingandy, repared air compressor. Fixed rear shade, fixed headliner. Nothing major. Most of work I did myself, except headliner and coolant replacement. I did not want to touch headliner: man got to know his limitations; Changing coolant is too messy and I do not have professional equipment. $300 seemed reasonable to have independent shop do it.
Service adviser suggested to change transmission oil as it is leaking and under previouse owner some of the bolts on transmission pan were replaced with some bolts that do not belong there.
I looked up at the transmission on lift and it does seems to be leaking; but then again, 4 weeks prior to coolant change I had spilled some engine oil when I was changing oil and that may be just that.
Never the less: shop quoted me about $1000 to change transmission oil. 18 years old, it is a piece of mind to replace certain things. I figure I can save some green doing it myself; two co-workers have car lifts and they may let me use one. All in all, parts, so far, to replace pan; mechatronics sleeve; fill plug; 4 valve seals, bridge seal; ZF fluids dozen original bolts; 10 coated steel helicoils, just in case threads were stripped under previouse ownership all that cost me about $300 @ FCP euro. What worrants $700 labor? Even @$150/hr it covers over 4 hours. Is it there something I did not realised?
Yes, replacing sleve may take some time to pry it off it is not as bad as replacing spark plugs in Subaru 6R boxer engine; I will have to watch for fitting shifter properly in mechatronics body; use torque wrench. Filling transmission at the end not an issue I do have oil transfer pump that runs off a drill and thermocouples that I can fit inside oil pan to monitor temperature.
Am I missing something?

That feels high to me. Refilling the transmission isn't a fun job, but it isn't that bad. The car needs to be perfectly level and you need some way to read the transmission oil temps (I use an iCarsoft OBD reader which can read the Jaguar transmission temps and other codes), and the refilling procedure needs to be done with the engine running within a certain transmission oil temp range which means you are pumping ATF right next to the exhaust pipes. I did burn myself once this way.

Some pointers from having done this previously:

1. there is not much room to get at the fill plug, you need a very short 8mm hex. I took a "L" shaped hex key and cut the short leg even shorter with an angle grinder; this fits and has room. The first time I took the fill plug off, I needed some leverage which you can get using a deep socket on an extension against the hex key.
2. before you drain the oil, make sure you can crack open the fill plug, but caution and see number 3 below.
3. with the engine off, the oil level is above the fill plug. If you loosen the fill plug, do not open it all the way when the motor is off. Once I did, and in the outrush of oil I dropped the fill plug.
4. a lift where you can have the car raised but still get in and out of the driver's seat would be ideal for this job; the factory procedure involves refilling the oil until it drips out of the fill plug, starting the car, going through the gears, and then filling it with ATF until it drips out when in the target temp range. I've done it on ramps and jack stands and its... not particularly fun having the exhaust pipes within inches of one's face.
5. as for the electronics sleeve, I would only replace it if it is leaking. They can be... tricky. I have a Land Rover LR3 (which also has a Jaguar V8 mated to a ZF 6 speed) and I was unable to replace the electronics sleeve, I just could not get the new sleeve re-seated. I had to flatbed the Land Rover to the mechanic and have them do it.

While you are looking for ATF leaks, one area of traditional trouble is the ATF cooler pipe hose crimps at the front of the car near the radiator. I just replaced the cooler pipes to address a leak in one Jaguar.

$1000 seems a bit high to me; this feels like a 2 hour job for a trained mechanic. One option you might try is going to a transmission shop (versus general mechanic) with experience on the ZF transmissions. Good luck with it.

@scooterforever Thank you very much! exactly what I was looking for! I did not know iCarsoft has transmission temp! Thanks for the tip!
One question: from my experience with 2001 BMW E46 straight RWD. If I would raise it up off the ground; start engine put it in a gear and let wheels turn, DSC light would come up because rear wheels turning and front are not. When you put it back on ground and drive for few minutes it will come off. So the question is: when jag is raised and engine running gearbox should be in park or neutral while it is worming up, right? Should I keep foot on brake while going through gears?

Do not let the rear wheels turn at any time.
Keep your foot firmly on the brake pedal.
While you shift through the gears, then let it run in park

+1 to Wingrider's comments. Also grab the factory manual for the full procedure. The iCarSoft model I use is the i930, like $120 on Amazon now. It has two modes: Jaguar/Land Rover diagnostic mode which I use to access the transmission details as well as suspension and other error codes, and regular OBD diagnostic mode which I use for for check engine lights. If you search this forum there are other OBD readers I think that can do it.

Another idea if you don't want to do it yourself is to talk to a BMW specialist... they will probably be familiar with the ZF transmission though they might not have a way to read Jaguar computer ATF temps.

@Wingrider , @scooterforever Thank you, gentelmen!
I already have all parts, I have i930 and bunch other usfull stuff, like indispencible 5# 'convincing' sledge for stubborn fill plugs and stubby L-shape Allen wrench. I will do it myself, there are not many occasions I can make $700 in half a day on weekend and have beer with coworker talking cars afterward.
Not to mention it gives me a bragging rights!

Mercon SP transmission fluid is the same fluid.
Except its red, & costs less, both made by Shell.