Audio Systems: 92 lincoln continental, no tuner response, premium sound system, ford lincoln

Question
Trying to figure out why there is no sound from radio when tuning in a station on a 92 Continental with factory installed JBL radio. The cassette player works just fine. The antenna raises up when radio is turned on and you can scan to find the stations but no sound.  Someone said there might be a seperate tuner on some Ford/Lincoln that would probably be in the trunk. Have you heard anything about a seperate tuner being used and how can it be fixed or replaced?  What about installing a aaftermarket unit, would the antenna need to be reran directly to back of unit?
Thanks for any help you can give.

Answer
Yes the radio is probably shot, and here is a good start on how to install a new one.
http://www.installdr.com/InstallDocs/FLM/PDF/356001.pdf

You absolutely should spend the extra dollars on the integration adaptor for the premium sound system, without you will have to make an amp bypass jumper, and that takes even more time.