Hi there
If it's been sitting for a while get it sparked up and see if it holds its level. It will probably be fine.
Pumps are much more common than legs, I've got one to do this weekend on a xj6.
Be careful of values; A very nice 4.2 will pull in decent money on low mileage, but other engines aren't nearly as valuable.
Getting one forecourt ready might be a nightmare. Making sure EVERYTHING works on these was hard enough ten years ago, let alone know
Ultimately you're going to end up putting in more time, money and effort than turning a hatchback, I know I should stop messing with them, but I love Jaguars.