Jason, It really boils down to whether or not you trust your overhaul shop. The TCM overhaul manual specifies both "new" and "service" limit dimensional tolerances for all parts. Some shops insist on doing all work to "new limits" and some are OK with a "service limits" overhaul. If the work is done properly, both approaches are fine. Cases on the 520 series engines have a history of wear and cracking problems, so it is entirely possible that your case is toast. Most quotes do assume that the case and crankshaft are serviceable and better shops all write something to that effect right in the quote. Why don't you ask the guy what was wrong with the old case? If there was fretting wear around the bearing bosses or unrepairable cracks, ask him to show you or send you photos. Ask what Divco would charge for a crankcase repair or for an exchange crankcase. Some shops will look for any excuse to sock a customer with price increases, but most are genuinely concerned about quality and your safety. I would add that engine break in and several hours of test flying should be included in the overhaul price. If you don't trust the engine shop to be honest with you, how will you feel flying your family behind that engine in crummy weather?