Looks like the shifter lever just popped out of the slot (#7 or #11) on the shift fork and it's stuck in whatever gear that was engaged at the time.
Should be a matter of taking the shifter cover (#1) out, slide all the slots (#7 and #11) to the middle with a screw driver as pry bar, this will put it in neutral. Then put the cover back in while putting the rod in the middle of the slots at the same time.
Pay special attention when assembling the shift cover as it is what holds the PTO brake in place, check the right picture I attached.
It's not an hard job but if you're not mechanically inclined at all, it might be a bit complex. It's possible to leave two gears engaged at the same time during the repair which can mess things up. If you don't feel comfortable with that, it's better to send it to the dealer or have the dealer or a mechanic come to fix it.
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