For the gear box I would recommend something along the lines of Motul Gear 300.

Maintenance is going to be like any other motorcycle. Chain, tires, brakes, oil, etc..

With a 2-stroke you then got things like checking your oil injection system, spark plugs and RC Valve system (Exhaust valve pullies).

Oh and wheel and stearing head bearings are always good to check on these older bikes.

As Fontyyy mentioned, there is no Honda manual in english, so its sites like this to help you out.
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Charles Gallant