project moped manual has the a35 shop manual, start by grabbing that, print it out so you can easily reference it. read through the whole thing so you know what you're getting into.
a35's are just about one of the easiest moped engines to build but there are still a few pitfalls. pay attention to keeping all the shims and spacers on the shafts in order.
i would at the very least replace your crank bearings and seals, and the two small bearings in your side cover, new gasket set.
that said, if it aint broke dont fix it. maybe pull your clutch cover first and see if any of this is necessary, might be something else wrong with your bike, rebuilding the engine for no good reason is just an opportunity to fuck shit up. Same with the ring, i usually get 4-6k miles out of a set of rings on a chrome kit, unless its been seized or overheated a whole bunch you probably wont gain anything just replacing that for fun.