Snowblower stuck in gear

The issue here is likely related to the "linkage". Linkage is the parts (often a cable or metal rods) that connect the shifter to the actual part(s) inside the snowblower that need to physically move to change speed and direction of the machine.

You'll need to carefully inspect the entire linkage to locate missing or worn cotter pins, bolts, etc. You may need to open the underside on the snowblower to inspect and access the entire linkage. These are typical parts that are used to keep the linkage connected to the shift handle and internal wheel assembly. The linkage isn't usually complex - often a pin or threaded portion that passes thru a hole in an assembly - that is held in place with a cotter pin, bolt, etc. Simply move the shifter so that the linkage can be secured properly and you should be "good to go".

Good luck!