91 Sonoma Wiring Problem

i just picked up a wicked deal on a 91 Sonoma .. 5 spd blue in color and its only got 54k on it, but the only problem is that for some reason when I open my door (it causes the floor lights to come on) and the radio cuts out, also if i turn on my dome light (it causes my floor lights to come) and the radio cuts out, although when i turn on the dome light .. the cab dome light up top does not turn on, but if i plug the cigarette lighter in (the floor lights dont come on) but my radio cuts out and the dome light then comes on .. this seems very strange, i imagine im going to have to search for a crossed wire or something but if someone could give me some help, it'd be greatly appreciated, i dont know where to even start looking.. thanks a lot

Get a wiring diagram (Haynes). Try to see which wires are related. Sounds like a plug in connector.

Get a wiring diagram (Haynes). Try to see which wires are related. Sounds like a plug in connector.
what do you think is wrong with the plug in connector? not connected completely or loose wire? or what? .. I also forgot to mention that all this has happened since I got the truck, although I have not many even the slightest modification to the truck, just been driving it, also my horn does not work anymore, it also worked when i got the truck .. it just buzzes and cuts out the radio and (oddly enough) turns on the dome light

Connector could be loose or corroded.

i had this same problem with my 91 sonoma all it was was a bad fuse once i changed that everything was fixed