Its above the transmission, closer to the driver's side. Follow the wiring from the sensor to the plug with your hand, you'll find it.

 

Yes, on top of the tranny, great place for it huh? You basically have to plug and unplug it blind. It will help to look at the new one, but for the most part, if you reach up and grab the whole connector, you can pull it out from the mount first, then you can move it down enough to actually see the plug.

 

wd-40 doesn't work that good on stuck threads. CRC makes a penatrating fluid called knocker loose (comes in an orange can) and from what i've seen it blows away liquid wrench, wd-40, and pb blaster. just spray it on, tap it with a wrench or hammer (something metal) to work it into the threads and a few minutes later it'll seem like it wasn't even stuck. i just did my shocks and gave all the bolts a shot and a tap and went back to it 10 minutes later and the bolts felt like they had just been tightened down and didn't have any rust on them.