'82 Sedan DeVille ?'s

whats up ppl I just bought a '82 deville. its been sitting for 2 years but otherwise its in great condition. i have been going thru and changing out some parts- cap and rotor needed replacement, gas pump went, thermo stuck, i guess its just because it sat for so long. but right now i have a prob that i cant diagnose, i think its something electrical but not sure- when it idles it almost stalls then jumps rpms, and inside the car the gas/mileage gauge reads some crazy numbers and skips around from average mileage to the other 2 readings(cant remember what they are), and the check engine light flashes. when i bought the car a rodent had gotten inside, there was acorns and droppings in the glove box and trunk, could it have chewed wires or something?? or is this a different prob?? timing?? also, i have what seems to sound like a vacuum leak inside the car under the dash when the car is in gear, and the parking brake wont let loose by itself. is there a vacuum line aroud there somewhere that i need to change?? also, when i hooked up my cd player, i used a wire harness and when i turn the car on it gets power, the antenna goes up, but when the seatbelt light turns off the cd player turns off and the power antenna goes back down-wtf?? so i just ran some wires from the fuse box, but maybe this has something to do with it??

Check all your vaccum lines, vaccum lines cause my car to run so bad its like your in a vibrating chair while your idling.