You didn't mention what year,but if it's an 89'then the problem could be the
chime module.
Module is located (on the 89')on the left side of the fuse panel.
It controls the buzzer you hear when you leave the keys in,seatbelt not connected.....yadda yadda yadda.
Pull the module,put another fuse in and see if the inst pnl lights work,along w/radio,if they do then that is your problem.
Removing the module,there is a release tab to the left of the module,and removing the module DOES NOT AFFECT ANYHTING other than the buzzer.
Buzzer=
Lights on
Key in
Seatbelt
If you want to relplace it,I think it's a dealer only option,so that means $$$$$
how much I don't know,I had the same problem about 1.5 yrs ago and it cost me $130.00 to find out it was something I could of done myself.
If you pull the module and then find out that inst pnl STILL doesn't work then your issue is in the wiring somewhere and you will need to start tracing with a multi meter or have some do it for you.