Ben, the first question is why you think the rings are worn. Have you tried putting a spoonful of engine oil into the spark plug hole then pulling the starter cord, to see if compression has substantially increased? If it has, you need new rings. If it hasn't, you probably don't. Is the smoke from the engine blue? If not, it is probably not oil smoke.
Should you decide you need to replace the rings, I suggest you service everything covered in the owner manual, clean the inside of the crankcase, inspect the crankpin and connecting rod big end, and test the ignition, the only other thing you could consider doing is cleaning out the carburetor. I don't actually recommend that though, unless you've had considerable practice already. The average home mechanic probably does more harm than good to carburetors, unless they are actually misbehaving. Why not replace the rings, service it, then try it to see if everything is working properly? If you aren't satisfied with the way it runs, let's talk about the likely causes and some targeted work to put it right.
