Would a blown head gasket be evident before replacing the transmission?

What is your question?

I had got into an accident in 2013 on a snowday. I ran over stack centerblock that was covered by snow and it tore the splash plate off in misaligned the bumber. Later I had discovered that my radiator was cracked and it had blew my transmission. I had the transmission replaced at Cottman's transmission and when they completed the repair and test drove the SUV, they notified me that the head gasket was blown. The repair cost for the transmission was about $6,000 and I couldn't afford to have the head gasket replaced at that time. My question is would that repair shop have knowledge of the head gasket being blown before completing the transmission repairs? Also the vehicle has about 145,000 miles so what other componets should I expect to replace while getting the gasket work completed (i.e. timing belts and water pump, piston rods, etc). Thank you.