Overheating?

Hi so my 2002 Pontiac grand prix is overheating once again we changed the thermostat and radiator cap the first time it started this. Its overheating only when stopped liked befor also we kept driving it and eventually it just stopped over heating untill the other day when we noticed brown gunk on the radiator cap. We flushed it out and got the brown gunk out now it overheats again any suggestions ?

I never used a sealer at all and to flush it I used prestone im assuming the gunk in there was blocking the problem so it didnt overheat now that its out it overheats again. Maybe a water pump?

Also there is coolant in the oil so I dont think its a blown head

On a long road trip I recieved the low coolant message. The town I got the coolant in did not carry the proper DEX-COOL antifreeze/coolant so I purchased a bottle of normal antifreezecoolant. After a few more hours of driving on the freeway (Average speed was about 70 MPH) I noticed the white smoke coming from the tail pipe. The engine was at normal temperature but I knew something was wrong because of the white smoke. I added more antifreeze but continued to lose it fast. The car seems to run fine but still smokes. I read an article that said the first step is to remove the intake manifold then inspect the gasket. My main question is the car safe to drive until the dissasembly occurs and repairs are made. And how difficult is this process? I have not done a whole lof of car repairs but can usually figure stuff out pretty well. Or should I leave the repair up to a mechanaic?
Thanks,
Brad

Any other suggestions?

Im sorry I meant there is NO coolant in the oil

Car starts beautifuly the first time of the day. Go to start it again and it starts but when driving it would have issues. As I was driving it would randomly die. So I took it to advanced auto to read codes. Car was misfiring so I changed the ICM which fixed the misfire. Then the car ran good the first time. So o checked the fuel pressure and it was only at 30-35 psi. So o changed the fuel pump. Drove it for about 20 minutes and it was back to its old habit of trying to die while driving. It'll start but when it starts acting up the tachometer jumps and so does the fuel gauge. The low oil light, change oil soon, low gas, and battery light all come on. I can sometimes get the car to come out of it by putting it in neutral and try to keep the rpms up. And other times I can drove with two feet and keep the car running but sometimes it'll just die. The ignition switch is broken. Would that cause the anti theft to come on at certain points and kill the car? The car runs great til it gets warm/hot and then I start having issues. It doesn't overheat. The head gasket is fine. Any help is greatly appreciated.

There is no coolant in the oil I meant