any one can help on car cd player

im wanting to install a cd tape combo oem radio in my car it has reg tape deck car is cadillac seville 1996 both radios have same factory plug but cd replacement dont work
Your situation seems easy for a good car audio store to troubleshoot, but difficult for audiogoners, especially via forum.
would not swear to it but I think radio in your car must be set up by dealer with tech II tool
Delco made a tuner/CD/cassette double din combo unit (Bose) in the early '90s. Might fit your Caddy. Ebay? Junkyard?