I'm all for used parts like everyone else but here's a little advice on this one:
-This part sits in hot oil. 1991 was a long time ago and any used one has been baking along for over 20 years.
-The wires that exit the case commonly get very brittle and tend to break. This is the most common failure point so check yours first. They break at the grommet where they exit the case.
-Along with this part: invest in a new gasket for the case. You can use RTV but it's hit or miss if it will seal completely.
-Used electronics are always a crapshoot: sometimes they're great, other times not so.
I'm only telling you this because I've repaired two and had the actual bakelite crack and short where the reed switched is housed inside the motor. I ponied up and replaced it with a new one to not have to deal with it again. It'll leave you stranded and there's no way to rig it to get home. Ask me how I know.
My .02$.
-Randy