new celica and trying to get help with the couple problems i have with Options

[Stallion]

hey, got mine back in june, its a 94 gt hatchback with 185000 miles. shes been around thats for sure but still runs REALLY well. im not worried about her breaking on me but there are a couple things that worry me

1. when braking or accelerating sometimes i hear a small pop kinda like a joint from the rear.
2. when i turn on the ac it makes quite a bit more noise than ac should
3. i have a sub hooked up and a 600 watt amp. sometimes when i go to turn on the car itll fail so i just rev the engine a little and put it in gear

anyone know what i need to do to deal with this stuff

and on a side note anyone know any san diego places that WONT rip me off on body and repairs? i got a couple dents that need pushing out and the front bumper needs to be pulled out a bit on one side and the cracks fixed