I just had the same repair this last week. I hit a paver and the chain derailed. The event also sheared the auger drive pin. (bolt)
The master link MUST be undone to get the chain over both sprockets!
Bit the bullet.
Detach the blower from the tractor.
Remove the shield.
Loosen the bearing support.
Use a paper towel or two to wipe the lube off the chain.
Locate the master link and roll it to the top sprocket.
Remove the link plate retaining clip with a common pliers. One jaw goes on the link pin and the other engages the open end of the clip. a squeeze releases the clip from the other link pin. The retaining clip may still hold to the other pin, so turn it 90 degrees to better see what it takes to get it off.
Remove the link plate from the pins. Push the Master link half through the two chain link holes. The chain is separated and may fall off the sprocket to the ground below.
Fix the sprockets as needed.
to reinstall the chain over the sprockets, it helps to twist a length of soft wire onto one end of the chain. Thread the wire down,around and back up over the sprockets. double check the chain is laying true on the sprockets. With both ends of the chain at the top, place the ends onto the sprocket and insert the master link half through the chain link holes with the removable link plate side out towards you.
Assemble the master link.
Lightly snug the bearing mount plate fasteners (4). adjust the chain tension not overly tight. rotate the entire blower mechanism looking for the tight spot in the chain travel.
Adjust chain tension, and tighten the mount plate fasteners.
lube chain
Install cover (2 cap screws)
Test rotation again! (don't ask me why ;-)
Refit the blower to tractor and give it a go!
It took me an hour.
eta
I had thought to remove the bearing plate fasteners completely. I'm sure the chain could be fitted then. But there is no finger room to refit those lower carriage bolts. PIA! So no, I didn't go that way.
cheers