Joe,
yeah, it sounds to me like a head gasket but it could be a lot of different things. Did it overheat because of the head gasket or vice versa? It could be the block being 'decked' wrong or the head being warped, etc. They did something wrong most likely. Your engine is probaby OK but it depends on how long it was overheating. I know what the Shop probably told you- that it was your fault because you let it overheat. Typical, always blame the driver and never take responsiblity for their own actions. It sounds to me they messed up and not you. Call me if you want but let me know either way what you do and good luck..............