I have an 00 GTP and there is nothing under the starter blocking my way to access it from under the car. Simply jack up the car, remove 2 bolts holding starter to motor, remove the starter wires and it's off.

So to be clear about your post, you tried jump starting the car and it still just clicks? Battery has a full charge?

Crank position sensor can keep the car from starting if it has completely failed, but it won't keep the car from cranking over and trying to start.