Low oil pressure

[SupraDupra]

I took the supra out to an empty parking lot and delivered a real beating to it.After about 10 minutes and a lot of attention I decided I should leave before the cops came ,but I noticed I was reading zero oil pressure and the temp was higher than usual.I shut down and checked the engine over and it was purging a lot of coolant.I tried to start the car just to put it in a parking spot but it wouldn't start.I went to dinner and came back when the car was cold ,it started after some effort and the oil read about 18lbs (as it usualy does) and I headed home.When the car got to operating temp the pressure got very low ,about 3-5 lbs.and the car died just outside my driveway and wouldn't start again untill it cooled down.I was told that if I just changed the oil it would likely cure my problem ,but that sounds too easy to be true.

Also ,would it be possible to remove the engine mouts and jack the engine up enough to drop the oil pan? If I could change out the bearings down there without removing the engine I would be a happy man :P