I suspect the mechanic tossed out the warped head diagnosis to ensure it was understood that a resurface is mandatory for a good repair. The block deck needs to be checked for flatness, as does the head. I would be surprised to see a head that had a gasket failure, especially on an inline six, not show some surface irregularities.
It is a pretty easy fix. As mentioned parts are plentiful and inexpensive. I have seen several running motors in the $400-600 range recently. Depends on the condition of the rest of the car though, and the current owners lack of desire to make repairs I guess
Current ride... '13 GTI Wolfsburg
BMW's from my past...
'92 535i/5 '89 325ix/5
'98 750iL '86 325(e)/5
'95 740iL '84 318i/5