I have done a number of larges sales like this both as seller and buyer. I always insist the transaction be done at MY bank. His credit union should be able to transfer to another bank. The bank will have people that will see all the proper paper works done.
I bought a 28ft cabin boat in OK and just went to a bank there. My bank in NM sent the $$ to the OK bank while I waited, the seller was able to get his money before he left. I paid a notary fee and the bank checked the titles, had bills of sale etc. When I got back to NM I had everything I need to get the boat & trailer put in my name except a required sate VIN inspection. (Any type vehicle brought to NM is required to have a VIN checked) Doing the transaction in a bank insures it's done right & no one gets screwed.