I have a Delco CD chager in my 98 Lumina LTZ right now and was wondering if there was any way to hook it up to my stock HU in the 93 SSEi (cassette with 5 band eq) ? Or can I switch to a newer (96+) HU and still keep all functionality?

No, not unless you use an RF modulator. I'm not sure how they are compatible with the newer head units, but those head units are not a completely direct fit.

http://www.bonnevilleclub.com/techinfo/?article=58

I was reading somewhere that the 92 had an option for a cassette deck that had a multi disk cd option. I was wondering if anyone had this and if you had a CD changer?