$2700, 3 weeks and a dead car

The car I was driving was do for major engine work. Neeeded new timing belt, value seals and such and realized that the cost of these repairs would be very high and the engine itself was not worth it due to it high miliage.
So I decided to have a completely rebuilt engine put in it's place.
I searched around and found a company that not only had this type of engine (in completely new/rebuilt condition or so they said) and would install it for me.
I brang in my car, which was running perfectly everyday, for the work.
Typically this job requires 3-5 days for a (competant) mechanic. They staed it would take about that long. Also we had already areed on a price, but they called back and asked for some $300 extra for "other needed parts" - I agreed to pay it for I just wanted a job well done.
Date I droped off the car, 12/31/07 - day I got the car back, 1/08/08.
The same day I got the car back, I broke down in the highway, forceing me to tow the car to my home. The next day, they had the car towed back to their business.
They found "unforseeable problems" and took their time fixing it. I ask for a loaner vehicle or to get a rental at their expense since the fault was theirs, but they assured me it would only take a day to fix. Date they towed the car back, 1/09/08, date I got the car back, 1/16/08... forcing me to take 3-hour train and bus rides to my job (thats one way).
On the 16th when I got the car back... it was a little better at first, but then left me stranded again short of my home... the car barely limped to my home.
It is barely in running condition and I do not believe they did the work they say they did at all... and if they did, then its the most shoddy and unproffesional work I have ever witnessed in my life.

What are my legal options here... I dread returning it to them for the third time as I cannot afford for them to hold it another 2 weeks.
And I am still now left with 6+hour a day commutes to work and a wallet that is lite $2700 as payment for completely ruining my car.

Based on what you say here, you could file suit against them (or at least threaten to do so) in small claims court or in regular court; filing in small claims court is easier and requires no attorney...you could try to collect all of the costs and damages that you suffered due to their behavior... You may also report them to your state attorney general's office.