Think about fixing it. I am going through the same thing. Look at the post 400 starting problems. It was the main bearing. the rest looks brand new. I bet you can fix it for about 500.00. If you do the labor yourself. I am getting plenty of help from the good people on the site. Good luck.
The first dale I ever got to work on was afx400 with the flywheel bearing failure. This was before Timbo was doing the updates on the case. We installed a ball bearing that fit in the hole but was a little underrated and put the engine back together reusing all parts. TOTAL COST WAS $22 The quad is still running but only runs a couple hours a year.
Of course I would never do that anymore without spend a couple hundred more updating the rest of the engine.