need help with what I think is a timing belt problem

Hello

I had my car in for a 60000 miles service last week, because I'm going to sell it soon! Everything was done including changing the timing-belt. 2 days later the engine runs bad and stops! I had to bring it back in, and one of the cylinders was broken!! I paid 2000 dollars for the service!!!!

So my question is: who is responsible for the damage! Isn't there any warranty on things like this!! what shold I do??

Andreas (new to this forum)