if ur using the car for an average daily driver i wouldnt worry about cracks especialy if it has alot of miles already. unless its leaking coolant or any other fluid from anywhere the block or running any different then u may have a problem and then u need a new engine anyway but if u plan on keeping it and eventualy doing some performance mods u may want to pay the money.(shop around u may find someone to do it cheaper) so if it doesnt leak make sounds or lack power it realy depends on the milege if its alot dont worry just wait til it goes. as for the gasket just replace it and leave it at that.