I'm thinking you could sell for 5k with no problem if you get the shift issue solved.
Can't you move it out of M when the engine is off? My 06 will get stuck in gear if i'm on a grade but I turn off the engine and can switch to neutral, restart and put it in whatever gear I need. Works like a charm every time so far.
Doggman has a post where he fixed his. It was stuck in reverse but it is the same procedure I believe. It is most likely the shifting fork- either out of place or bent. That is what happened to his.
5000 sounds like a fair price. Good luck . bordercollie
edit..There is a link to the shifting problem under the sticky thread at beginning of the RTV forum....but it wasn't working last time I tried it. http://www.nettractortalk.com/forums/showthread.php?t=11383&highlight=shifting+fork
Thank You Doc for a great site too!! I hope I never have to do this procedure but if I do, I will take lots of pictures- and post them !!! - OK ya'll- I felt those vibes- don't wish that on me ...please ! collie