vivekshar

Hey ,
I have a 93 GXE with 164K on it. It has been having this hesitation problm when I press the gas after stopping on a red light. Also the car was racing from 700 to 1500 rpm by itself in idle and at times even stalling . I read on forum earlier that someone had similar prblm due to power transistor .I checked the power transistor and I think its gone bad and heres why I think do..
I connected multimeter between points a (+ive) nd b(-ive) with at very low resistance and it shows nothing but when I connect reverse with b as +ive of multmeter it momentarily shows some resistance and then again no reading. But I guess it implies there is continuity where it should not be there.
Am and checking properly and am I correct in assuming my PTU is bad ?
If yes do I have to replace the whole PTU or just transistor. I can see 2 screws and third at the base .Do I have to remove all 3 them to replace . Does anybody have instructions on how to replace it ? How much does a PTU cost ?