RepairPal Certified shops can diagnose and repair your 1996 Cadillac Seville. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.
"Climate control system" means "air conditioner". He must be saying your entire AC system needs to be replaced, which is weird. Perhaps he means the computer that controls the air conditioner.
Either way, it will be very expensive!