Someone on this BB has submitted a detailed prcedure for this repair. I did mine last winter. Kestas is right, removing the seatback is the most difficult part; that and the structure inside is apparently manufactured by Gerber knives. I cut the heck out of my hands in there.

I salvaged the old plastic gears. Using several plastic ratcheted tie wraps, reattached it to the seat frame. Got the idea from the post.