Toyota Repair: Over heating, head gasket leak, coolant leaks

Question
I own a 1993 Toyota Mark II Grande 2.5, V-6 with automatic transmission.  The mileage is 117,220KM.  I drove the car on a 3 hour road trip with the AC on and on the way back home it began to overheat.  Now it overheats after about 30 mins of driving.

Answer
check for coolant leaks and make sure the cooling fans are working.
if all is good you may have a head gasket leak.
pressure test the cooling system and see if it rises significantly as it heats up. If it does you can assume the exhaust has breached the gasket and is going into the cooling system,

Mike