As Denver said, bet thing you can do for your car is get the suspension checked over by John at Wheels World or Wilkinsons.

http://www.carscene.com.au/outlets/wilkinson/index.htm

The very first mods I did on my car were a WhiteLine Handling Package.
It transformed MY99 WRX. Dramatically reduced understeer, and the thing would actually point where I turned it. I think a package costs around the $750 mark new (including wheel alignment) or you could always source the parts 2nd hand yourself. A cheaper option is just get a proper wheel alignment done.

I also suspect you have a massive toe out problem on the rear wheels too producing your oversteer problems. Other problems could be tyre pressures, what PSI are you running front/rear ?

Get you car sorted before you even look at driver training.

Jamie.