Nice save!
There's a sticky at the top of the column here on how to clean older machines. It's a very good place to start.
I don't know much about Minnesota machines, they may be an old Sears brand. Others here can tell you far more.
Use sewing machine oil or Tri-flow-a light synthetic oil to clean and oil it. Other oils can be too thick, damage the finish, or both. Don't use products like WD-40. They're not a good long term lubricant and some may damage the finish.
The black finish is actually japanning, a type of baked on finish with decals applied then a top coat of shellac to protect the decals. Strong solvents will destroy your decals. Water might too if the top coat is damaged.
Your best bet for the missing drawer handles would be new drawers from ebay or possibly members here. You can also get new treadle belts there.
Glenn has a tutorial on restoring the finish on the cabinets in the tutorial section of the forum.
I think you have a very good find and I expect it will clean up very well for you.
Rodney