Jaguars are a labor of love.
I find that if they are well taken care of the are reliable.
Not sure on gas mileage, my 1993 gets about 18mpg.
No. I have had a 1998 and now a 2000 XJ8 and paid less for both then what you are paying for a 4 year older car 6 months AFTER I bought the 2000 with 88k miles.
In any case you can do better - and it would make sense to get the better engine - go 2000 to 2003 if you like the body like I do