Number of problems/questions, first time car owner.

[Demorphius]

Hello!

Before I begin, I'd like to say that I'm a first-time car owner. My Focus is my first car, and I've been driving it (and loving it) for three years now and has been by far the best car for me. It's great on gas, it has plenty of cargo space, and it hasn't given me a single problem until now.

So the car is a 2001 Focus ZX3, 98k miles. I'm the 5th owner of this car, and I've taken very good care of it. It's been my best friend until the past few months, when small problems have begun to arise and being very car-ignorant I don't know where else to turn, and I'd be extremely thankful for any help I can get. ):

I had a car crash (head on) on July 2007 and as terrible as it sounds, my car took the least amount of damage. Cosmetically, it only got a scratch on the front bumper while the other car was.. Rendered useless to say the least. Mechanically, as far as the mechanics that looked at it, only lost one fog light that was replaced. Since then, the engine has been vibrating very badly when cold, and I've had that looked at by a few mechanics, one of them a close friend of mine, and none can find anything wrong with it. They simply blame the bad reputation American cars have. Once the car is at a normal temperature (needle in the middle) it doesn't vibrate at all, unless I turn the A/C on, which causes the steering wheel to vibrate quiet a bit, especially when the car isn't moving. Also, it makes the car almost stall when moving at very slow speeds in parking lots. I've seen the needle drop to a little below 500 RPM then jump back up to 1k. Recently it's been overheating a lot. The coolant is never empty and I've made it a mission to check it weekly. If the car is running on the highway it hardly ever gets hot, but when driving in the city it's a huge problem. Once, parked in the shade for roughly 5 minutes I wasn't paying attention and it began to smoke a little, so I turned the heater on full blast until it cooled down and I turned it off. Also, if the A/C is running, it never overheats. I don't know why, and right now I can't afford to take it in to have it looked at. If anyone has any ideas, please do tell me. I'd love to do any repairs myself, but I rent and I can't do any mechanical work on my car in the parking lot. I've gotten yelled at by the building manager for putting fluids into my car. Haha..

Any help is greatly appreciated. Also, if you wanna see pictures of the crash I'd gladly post 'em. ^ ^


***EDIT***

Completely forgot to add this bit!!

Since I bought the car, there has been a huge problem with the A/C leaking water onto the passenger side. When I bought it, the car had no warranty, and mechanics told me I needed to take it to a Ford dealer to have that fixed, but warned that it would be a very pretty penny, so I never used the A/C until now that the car overheats without it. Well, it doesn't leak into the car anymore, BUT!! When I accelerate and the car is between 1st and 2nd gear you hear water inside the car, around the middle of the car. It sounds like air passing through water. I'm extremely worried about what that might be, but as I said above.. I'm broke and I can't take it in.. Any ideas? My biggest fear is that somehow water got to where it shouldn't be..