Looking for help regarding engine compatibility.

I have a 2003 base model X-Type that originally had a 2.5, also has a 5-speed manual tranny (which I love).

A little history before my questions. Two years ago when the timing chain went so I decided to check into switching to a 3.0 since everything I could find revealed the only real difference is the displacement and you have to take the engine practically out to install the new chain. Bought the engine from a local yard out of another 2003 X-Type that they said had 94,000 miles (more than I wanted but went with it). Had mechanic make the switch without problems, except that I didn't notice big power boost that I expected based on what I have heard about the difference in engines, but it ran fine for two years.
Over the past six months, the 'new' engine started using or burning oil and last week it died. Mechanic says its shot, not sure of specifics but not worth taking all apart to find out.
So here I go again, decision time. Not sure if I should spend what the car's worth to swap out engines again, although the car is only worth scrap/parts if I don't and I really like the car, especially the 5-speed stick which have become difficult to find nowadays (in any car).

Question 1: IS THERE ANY COMPATIBILITY ISSUES WITH THE LATE MODELS (WITH HARNESS, ELECTRONICS, ANYTHING)? I found a 2008 3.0 with 60,000 miles which I expect would give lots of life left to this car. As a side question, not sure what the VIN and the 8th digit have to do with anything but all the engine posting seem to mention it. ?

Question 2: HOW MANY OF YOU OUT THERE HAVE HAD TO CHANGE TIMING CHAINS AND AT WHAT MILEAGE? If I go with this engine I'm wondering if I should change the chain (at just 60,000 miles) before installing. My mechanic says its a common issue with these engines.

Question 3: IS IT BEST TO KEEP THE ENGINE CONTROL MODULE THAT CAME WITH THE CAR OR TRY TO GET THE ONE THAT WENT WITH THE REPLACEMENT ENGINE OR ONE FROM A 3.0 AT LEAST? To me, it shouldn't matter but I don't know enough and wonder if there's any way it inhibited power somehow with the 3.0 I put in last time.

Thanks to all you knowledgelable Jag guys and mechanics out there, and those who have been thru this kind of thing.

 

With regard to the X-ype, I haven't heard of any major changes to the engine across all the years produced. There are transfer case differences. The biggest single change is that iin the second quarter of 2004 they completely redid the electrical harness for the X-Type. As far as removing and transplanting the electronics I would advise against. The changes in software upgraded would create a lot of headaches for programming.
If at all possible I would retain the throttle body and all original electronics. You would need to visualize compare the engines side by side and any differences I would go with your original components. E.G., throttle body, air intakes etc.

 

Like avern1 said, no major changes were made to the engines over the years in question. So, there should be no issue with unbolting the old engine and putting in the 08 engine.

As for timing chains failing, I have heard of a few, but there are always a few. I had 188K miles on my car and things were still tight. Granted, I was not one to continually run the car up to redline either. I tended to let the 3.0L engine do what it likes and make the low end torque. It is the high RPMs that tend to be hard on timing chains, especially when you get it up near redline and then hit the next gear quickly. That puts a lot of stress on the chain and the tensioners.