Over heating replace cam thermo and head gasket

Do the fans even start when the engine gets hot

wow, no year stated.!?? no location, no night time temperatures.?
ever to the work>?
costs vary by country, state and even the town.,
parts and labor.
before the gasket blew, did you run 50% antifreeze, and check it
each fall for 50% with the$2 tool> and 5min work?
if not , you will crack the head or block, (unless in key west .FL)

costs vary too, by what is wrong?, most times there are far more things wrong.
case in point, Rad leaks, hoses shot. water pump bad, and leaking
green at pump weep port. (signs)
new head gasket.
here is an example.
mech removes head , finds 2 head bolts snapped and 2hr wasted hrs.
then finds the head warped, (ask, measured .005" is bad)
then tests the valves and they leak (ask how) so sends it to the
machine shop and its $350 to grind valves and get head not warped
(heat relaxed and milled and pressure tested )he then installs the head, and times CAM and such.

as he puts on hoses, 2 snap in half, so asks owner, owner says,replace only the 2 bad hoses and ignore, the other very old
and near cracked hoses, mech rolls eyes,,,
flushes rad, new coolant, checks for leaks , it runs.

90% of all just head gaskets changed, fail, fast because all the checks were skipped.":
warp check
surface condition on deck and head.
cracks not seen or pressure tested
valves bad. and ignored.

so the cost can be as cheap as $25 , DIY, gasket
or $500 . DIY, (head bad)
not DIY , labor varies, can be $500 alone.

White steam/smoke coming out exhaust, oil in radiator, coolant in oil, smell of exhaust coming out the radiator, spark plugs wet with coolant, a coolant pressure test would confirm bad head gasket.

with cold engine refill radiator, leave cap off, crank engine if water spurts up out radiator is a head gasket or head fault, these heads are not resurfaceable new head would be required

THE CHEVY 3.8 A GOOD ENGINE BUT YOU CAN;T LET THEM OVER HEAT EVEN ONCE THE INTAKE MANIFOLD IS ALUMINUM AND TENDS TO WHORP CAUSING THE HEAD GASKETS TO LEAK IN TO THE CYLINDERS ANTIFREEZE YOUR T STAT IS LOCATED ON TOP OF ENGINE LOOK AT TOP HOSE ON RADITOR FOLLOW IT BACK TO THE OTHER HOSE CLAMP ON THE HOSE THATS WHERE IT IS ALTHOUGH YOU PROBELLY NEED A NEW RADITOR AND A COMPLETE FLUSH OF THE SYSTEM YOU MAY WANT TO THINK OF GETTING RID OF IT WHILE IT STILL IS RUNNING SORRY HOPE IM WRONG BUT YOUR T STAT IS NOT THE OLNY PROBLEM GOOD LUCK

Have you even considered the heater core? Have the heater core checked/replaced. As for the top hose collapsing...that is not good. Have the entire system checked out by a qualified mechanic.

Likely you are overtightening the housing. If you have paper gasket type, try using a double gasket. If "o" ring type, just use the gasket. When tightening the housing take up small amounts on both sides, alternating from one to the other. Tighten till it is firmly mounted but stop there. After filling system, check for leakage. if seepage is noted, take up on bolts one quarter turn or less till drip stops.always alternating from side to side. Unless you have the wrong thermostat in there this pretty much has to work.

thermo is on top hose opens to let cool water in once hot water has activated it so yes it will be on top hose on block

Try first to fill up the radiator while squeezing the top part of the radiator hose to clear out the air.  Observe once that is done.  this may be caused by a radiator cap that is not sealing the pressure correctly or some parts the cooling system that may let heat escape like radiator hoses that are not secure.  If they all seemed to check out, you may want to have your head gasket checked.

have you flushed out the radiator ? get some radiator flush and flush it out. There could be a blockage in the radiator.