Rotors are warping too fast...

Hey folks,
My 1st set of brake pads/rotors lasted right at 90,000 miles. I now have 156k on the truck and have went through a set of pads and two sets of rotors. the brake pedal has been super spongy. No where near a stiff as when I bought the truck. The stopping power has all but vanished when I am towing my Bass Tracker 18ft Aluminum (I've stopped towing it). Just have to take easy and not put myself in a hard brake situation. The rotors are warping way too fast. I can only assume the calipers aren't releasing all the way, keeping the rotors and pads hot all the time. I connected my Foxwell Diagnostic Tool to the truck and its produced the code C1246: Master Cylinder Pressure Sensor Malfunction. The weird thing is, the truck isn't showing any check engine/abs lights. I read on the TW forum that this code can be caused by jump starting other vehicles. Unfortunaly the dealer wants 3 grand to replace that part. I found some used ones on ebay for about $150.00. Would this be something that requires special tools to accomplish, if it comes to that, or is it a simple parts replacement and brake bleeding job?

 

As a side note, when you drive it, once you've stopped, feel the wheels and rotors. They should be warm but not too hot to hold onto unless you were really on the brakes right before you stopped. IF your calipers are hanging up, they will be pretty hot even after normal driving.