Poor radio reception, and non-working rearglass/wiper buttons

I have a 92 caprice that I have some some issues im trying to solve.

First my stock radio was working fine untill one day it just started to get terrible reception. I live a little bit out in the country/burbs and get no radio channels now. When i head in to the more populated city area ill get the signal with some static. Presumably the signal is stronger in the city thus my antenna finds the signal. I removed the bezel to remove the radio and i saw a port for what looks like the antenna. I dont have much experience with radios and sound systems but is this a sign the stock delco unit is dieing or can an antenna go bad? I'd like to keep things stock but if all else fails i have a radio out of a venture van to try. At the very least if it works still i can use this as a way to test if the antenna is the trouble.

Also the rear glass release and rear wiper buttons dont currently do anything. I got the car this way and in the glove box was a spare release solenoid for the rear glass. I have not removed the tailgate panel to confirm if its missing entirely never replaced. Anyone ever experience the buttons going bad? Over the years ive had the glass release spaz out but that was always from the tailgate button getting stuck. Also the rear wiper doesn't run or spray any fluid. I suppose this is a job for the multimeter.

While im in there with the bezel off it might be worthwhile to replace the warninglight bulbs. Anyones know what size they are?

The issue would lend itself to a ground problem. You really need an FSM to find all of the grounds, and what they go to.

Two of the major grounds are at the base of the driver's side A pillar behind the kick panel. There are grounds in the rear on the driver's side, and some others around the car. Your multimeter will tell you if there is power to the circuit, or if the circuit is grounded. If it has power and a good ground, it is the component. Sometimes a circuit will find a ground through another circuit if its ground is disrupted. A reading of some amount of resistance in a ground circuit is an indicator of a circuit finding an alternate ground through another component. When the circuit shares a wire to ground at a splice, or they are both grounded at the same screw, is usually when it finds the alternate ground.

Since you have the dash apart, you should be able to compare the bulbs at the parts store for replacement. You might consider replacing all of them, because all of them are old, and could go at any time. Be careful removing the cable for the gear indicator.

Clean the contacts on the back of the tailgate glass/ tabs they contact on the tailgate. If they get oxidized they'll cause the issues you describe.