Working on it yourself is the best option. Most here do that. Don actually maintains others Jaguars. An old member, Brutal is a Jaguar Master Tech. But most try to keep their x350 going.
I did not think you would fix all that at one run. Fix the leak, change the oil if needed. Service the two filters, and clean those water drains.
The plugs are inconvenient to change. Imagine the valve cover gaskets are too.
Get a scanner. As the engine control sensors age CEL’s will pop up and have to be cleared. Look for one that is designed for the 2004 model, some are not.
If you are a computer person! Have some old windows laptops (Win 7) there is factory software that is better than a scanner.
Since you have new tires go to an alignment shop. Find one with a computerized machine that uses lasers. They will know immediately if there is significant wear on some of the suspension components as they align it.
An alignment shop may be cheaper initially than the two you have been too. Definitely cheaper in the long run.
I am cheap, the shopI use charges 80.00for a four wheel alignment. They drive it after to verify steering wheel is centered. Machine is a Jim Bean or something like that. The laser really makes it accurate.

 

looks like a good price on the alignment. things wear out and if you can't do it yourself it gets costly especially on a jag. plenty of items on that list are easy to do