Cathy,
Was the bent top tension complete? If so couldn't you straighten the shaft? I've done that before with decent results.
JoAnn,
Parting out a 500 ...... ewwwww the poor machine. My #1 500 came to me missing parts. I brought it back to life.
I know, the parts had to come from somewhere. It this case the LSMG.
Bette,
The 500 tension is not overly complicated. I've watched your posts about this machine for a while and for the life of me I don't understand why those you took it too can't get it squared away. Maybe they think it's an International Farm All tractor rather than a sewing machine.
Just remember that if you do replace the tension unit, there are adjustments needed to make it work right.
Joe