Whoever does the work to your car has to pull the engine in order for them to put a new one in. Just get them to inspect the engine once they pull it out to see if the block really is cracked. If it's not, get it rebuilt by a good quality shop. You can get a engine rebuilt for almost them same price as a used engine and you don't have to worry about if it's been abused because it's pretty much brand new. Just my .02 though.
