My drain hole stripped out also. I went to napa bought a part that fixes this. Sorry I don't have a part number, so I will feebly try to describe the part. I figured I would use this part instead of trying to change the pan.
The part I bought has a big rubber piece on one end. Then a treaded stud come out of the center of the rubber end. On the stud, there is a metal brace that pivot's. Stick the threaded stud and brace into the stripped hole. then you can tighten the new plug up by hand. It seals the pan from the outside.
Later,
Zac