Hello,
Sorry to say, this will not be fun.
Read down this page for a decent write-up:
http://www.cadillacforums.com/forums/cadillac-seville-cadillac-eldorado-forum/682681-2000-sls-how-do-i-replace.html
RepairPal Certified shops can diagnose and repair your 2005 Cadillac STS. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.