1999 GMC Jimmy Radio question

All speakers worked well. About 1-2 years ago, the rear speakers stopped working. About 6 months ago the front passenger speaker would come on intermittently (and on a rare occasion, the rear speakers would come on). Now, only the driver side speaker will work. Occasionally, the front passenger speaker will come on and off.

The 1 & 4 buttons have the light blown. Also, the light is blown for the am/fm selector.

I've taken off the cover, pulled and re-installed the radio (i.e. to ensure harness is tight). Anyone suggest a fix?

could this be it?
http://www.automotiveforums.com/vbulletin/showthread.php?t=693667&highlight=delco+radio

It could be something like that for sure. Trace the wiring and see what you find. IF the spaekers are good and the radio itself is alright, you need to just follow the wiring and repair it.