I've refurbished a lot of gummed up engines. Get it out of the plane, the take off the carb, glow plug, and backplate. Soak it in fuel for a few hours, and see what has freed up. Turn everything that will a few times to loosen up the varnish, then soak for the rest of the day.
After that, you'll be able to evaluate the bearings. If the crank spins freely and there isn't any roughness or notchy spots, your bearings are fine. If there is, soak in another day while spinning the crank every few hours to see if it improves.
Use a thinned toothpick to clean out the fuel inlet and spraybar.
Put all new O rings and gaskets wherever they are needed. I've used regular copy paper to make backplate gaskets before. I've never had one fail. Gasket maker works too. Don't skimp on the O rings though.
You can often save the glow plug by soaking it and swishing it around then applying glow driver heat to burn off the contaminants and soaking again. You might as well do it while you're doing the engine. It's $7 you don't have to spend if it works.