'93 Taurus EGR sensor problem

While on the highway, my "Check engine light" came on (and the car started to run like crap). After awhile, drivability returned, but the light remained lit. Well, I finally got a chance to pull over and check...and found my EGR positioning sensor was melted completely away!!! :eek:
Now....before I buy a new sensor....what killed the old one (aside from extream heat LOL). Did the EGR go bad, taking the sensor out? Or did the sensor kill itself, using the EGR valve to commit suicide?
Also.....how do I determine the correct sensor? The local auto parts store lists several different ones. My car has the 3.8 ltr. motor.

Thanks

Steve