Engine overheating

[invaderdim]

I have a 1985 Eldorado and its having some trouble. Recently with the warmer weather it has been overheating while driving. It was happening above 75 mph and when I dropped back to or below 75 the coolant temp light would go back out. Now today(well yesterday now) I was on my way to work when the coolant temp light came on again, only this time backing off the accelerator did not help. trying to make it the the nearest exit, engine temp light came on and the car died. sat for about an hour and it started back up turned the heater on to help relieve the temp, but a block from work, the car blew up. one of the heater hoses broke, so I bypassed the heater. got it started drove the rest of the way to work. let it run for a bit and the coolant light came back on. I went to Pepboys and bought a new thermostat, still started to over heat. The fan is working, the water pump seems to be working, but still overheating. The oil is not any sort of milky, There is no oil floating in the antifreeze(although the antifreeze does look dirty) I'm at a loss. a friend said it's probably the head gasket, but I thought with that I would see oil in the coolant or vice versa. bottom line is there anything else I should look into for this, or am I screwed with a blown head gasket?