If you just want to take the chainring off, you don't need to pull the crank off. You just need the right size allen wrench to loosen those rusty chainring bolts. (Of course you may want to pull the crank to check and re-pack the bottom bracket bearings, but thats a separate issue. I did my conversion (also a mid-'80s Fuji) last fall, and haven't gotten around to doing the bottom bracket yet.)