1997 toyota 4runner
 

I have a 1997 toyota 4runner limited TRD. it is leaking on the backof the motor, I am thinking it is a oil pressure switch, how hard are they to change? does the oil pressure switch leak??
I also have had to have the brake rotors either replaced or turned every year (only had it 2 years) Just had the back brakes checked and they tell me that they are functioning properly, any ideas of what could be going on with my brakes, when I take it back to toyota or a mechanic, my rotors are always warped!!
I do not tow or have any steep hills where I live, I am at a loss and ready to sell it. any ideas would help.