Welcome! Good first post.
The 1994's are good trucks. My favorite year.
Do post up pics of your headliner and radio. If the headliner backing (it's pressed and molded fiberglass) is still good, recovering the fabric is a good DIY project. On the radio, it sounds like you're fixing to learn how to rewire a hack job. It's not hard; even a cave man can do it.
Brake lights- get a 12 volt test light; very handy to have anyway. First thing I'd do is to check for power at the brake light switch, on the brake pedal. If power is not there, look upstream and check the fuse next. If power is there, then look downstream at the bulbs, and also look at the wiring harness behind the bumper to see if it's been hacked into in the past for a trailer harness.
Good; between that, and finding this place, you got it made in the shade!