I don't know your specific car so I'm not an expert (but I play one on TV). I looked at pix of a 93 on eBay and it looks like the standard Cadillac dash plan. On my 90 CDV and 99 STS it was the same basic formula. You have to remove the 4 AC vent grilles (on my 99 STS they're held in by spring tabs that are a PITA to release and not break, CDV you rolled the vents down and they popped out). Once that's done there should be a 7 mm hex head screw behind each vent. Take them out, top of the dash pops up. There may or may not be screws around the defrost vent (for me CDV = yes, STS = no) and you may have to pull the A-pillar trim to get the dash top off and out (CDV=no, STS=yes). Disconect dash speaker wiring once the dash pad is freed. From there you should be able to get to the IPC and light switch. Someone else here may have experience with your specific car, but hopefully this should get you started.