car repair shops (wary)

I have taken my car to a shop, in disgust because it just waaasn't running properly after I left California. Needless to say, the shop has not done any work on the vehicle after it being there for three weeks. They demanded a deposit, and they say if the head is cracked, it will cost me an additional deposit of 1,000.00. Is this normal? They have my car that I love dearly, so why all the expensive deposits and the attitude from them? They also tell me that it will be an aditional three weeks before I can get the car returned to me as well. Should I be looking for another shop, or is this normal behavior on their part? Also, how much approximately is the repairs for the head gasket and stuff?