The big clue here as to why he SHOULD have the head gaskets/head bolts replaced is when he said:
"The coolant reservoir was empty, but the engine temp immediately dropped back to to normal. I let the engine cool for while."

The temp immediately dropped back to normal because the head bolts stretched and the head (s) lifted and released the high pressure. This is exactly what happened to mine too. I suggest having new studs in to replace the Ford headBOLTS, replacing the clogged oil cooler and egr valve & cooler...... I'd also take it to another shop to get a better estimate.