The 4.0l engine has en external oil pump. you have to remove the timing chain on one side, and then the oil pump can be removed and replaced.
This is a full weekend for a DIY project, but a few hours at the shop.
RepairPal Certified shops can diagnose and repair your 2002 Jaguar XJ8. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.