1998 Ford F-150 radio

Its usually best to replace. Those are all solid state parts in that stereo. Have you checked you attenna wires?
You can usually find another factory stereo in the salvage yards and getting them out isnt to bad either.
On the front of the stereo there are 4 small square holes. If you go to wal-mart they have a radio removal tool thats cheap all you do is take the 4 rods and stick them in those square holes and the radio should come out if you dont want to buy the tool you can take 4 thin nails and slide them into those holes and then pull it out that way.