Replacing crank shaft bearings?

I am rebuilding a 1972 Suzuki 550 GT (two stroke) motorcycle. The engine had 5000 miles on it by the previous owner, then it sat around in his backyard for a REALLY long time. It is now in about 500 parts in my basement and grage. The crank shaft bearings seem fine but should I reaplace them anyhow? It would seem prudent, is it something I can do myself?
Also, any advice on getting the engine case clean and polished would appreciated. There are about one million fins on the engine and cylinders as it is air cooled. I believe these parts are some kind of aluminum alloy. Thanks