What to do when a car dealership leaves a wrench in the engine, and more?

I bought a used car about a year and a half ago from a giant Subaru dealership. They told me it was a great car with a stellar service record and a single past owner. I inspected the vehicle thoroughly and could find no fault in their statements. Not a week passes and i begin feeling a serious clicking sound coming from the steering/suspension system. I take the car in and they say they cannot duplicate the problem. They ask me to show it to one of their mechanics and the minute the tech gets in my car he says in a rather aggravated tone "this is the one with the bad center dif". I reply that I had not been told that and he storms into the office to confront the writers who deal with customers. They put the car back in the shop and soon find the center dif to be bad (a very expensive and VERY rare repair on a subaru) and in addition recommend the rear brakes resurfaced, and the engine computer replaced. At first they claim I am responsible (keep in mind i bought this car less then a week before) and that i would need to pay a service bill of nearly ,000 - almost 2/3 the cost of the car. Finally they agree to pay and all is well.

A little bit later, the car begin dying on startup and idling very badly. They recommended the replacement of the O2 censor and a reflash of the engine computer (again).
soon after that, i went in for a brake job (again) and they said i had two major leaks in the head gasket and that they could replace the timing belt at the same time to save labor costs. I said go ahead.
so now were are caught up to the present.
I was driving up a small hill last saturday when i heard a whirring sound and then a horrible snapping sound. the accelerator stopped responding and the car died. I had the car towed to a AAA service center where they proceeded to find a damaged tensioner assembly, all three pulleys destroyed and the timing belt had jumped and bent multiple teeth. My original subaru dealership said they would cover some of the repairs since it was their fault for doing a bad timing belt repair job, but they would cover the entire thing.
the next day i get a call from the AAA guys who said they had completed the repairs, started the car and found two cylinders misfiring, then not firing at all. they took another look and found a broken piece of a wrench in the motor somewhere (a tool they did not use in the timing belt repair).
As of now, AAA is relaying their findings to my subaru dealership and they are in meetings to figure out what to do.

So to recap.
I bought a used car and within a year and a half have had: the center dif need replacement, the brakes need resurfacing countless times, the engine computer replaced twice and reflashed 3 times. the o2 censor replaced, a major head gasket job, now two timing belt replacements and now an enormous job replacing valves, and a few other engine pieces.

bottom line is i don't trust this car anymore and feel that this dealership has screwed me time and time again. They (stupidly) left a tool in my engine which caused major destruction, and have generally been confused, had bad communication and represented their brand VERY poorly.
My question is: is there a lawsuit here? if they don't pay up can i bring charges against them for this? what are my rights regarding this situation?
I am just so fed up with all of this that I want to do whatever is in my power as a citizen of this country to make this corporation feel the pain they have caused me (not to mention the rediculous amount of money i have put into this car)

thank you
i just wanted to clarify that i did not pay the ,000 bill at the beginning. they agreed to cover it.