MuGGzyx

I was searching for info on how to completely remove an old stock cel from the cars audio system and it occured to me that if all the wiring and mics/speakers were already there, how hard would it be to upgrade the system to accept a new style cel being plugged in or something. Assuming I could get the correct cords and such, has anyone done anything like this or would I have to get a full "modern" mobile cellular package?