How can i start a lawsuit against the mechanic?

I take my tow truck to the mechanic so he can fix the 3rd gear because it make noise, he told me that is the transmission and he will start looking for one, he told that he found a use one but he say is better to use a rebuild, i take the truck to the mechanic and are 10 days and he dont do any work on the truck he take the transmission out and he take it to other person to rebuild but he told that the bell-housing was crack and need to be weld, and told me that the truck will be ready this pass Tuesday, but the truck was not ready, i talk with the re-builder and he told that the main shaft is damage, i found lie from the mechanic, also i give him new clutch, flywheel and clutch pump, but i dont see any work done on the truck he said that he will have ready for this saturday what can i do