They don't even do that kind of work, yet they have come to the conclusion that you have a blown head gasket and your head is warped? What other symptoms have they found?
I would take it to another shop and get a 2nd opinion. Don't even mention that you took it to another shop.
YOU can do a little diagnosing yourself.
1. Check the oil level. Is it normal? Low, Overfull, or is it milky
2. Check the coolant level. Is it normal? Low?
3. Watch your exhaust. Is it smoky? Dark, blue, white? Does it smell sweet? Or like burning oil?
4. What are you seeing on your dash for actual temps? Is it getting high? But in the red?
Most computers will turn one fan on at 212 and the 2nd fan at 226. A/C on should turn them both on regardless of engine temp.
And never EVER use gasket sealant in the cooling system. It will seal other things up and cause more nightmares later down the road.
Your overheating could be caused by a sticking thermostat, clogged radiator(needs flushing), bad water pump.
1997 Pontiac Bonneville SEi-SCRAPYARD
2000 Chevrolet Blazer LT 4X4 4.3L
2002 Chevrolet *-10 LS Ext Cab 4X4 5.7 V8