OK! just to clear things up- The two stroke oil tank is on the right hand side of the fuel tank, on the MC16. the engine burns the oil so you need to keep topping it up.
The gear box oil is filled through the dip stick hole by the kick start. You drain the oil by removing thr drain plug under the engine.
only use top quality two stroke oil, i use motal or rock oil, fully synthetic. For the gear box i use 10w30 car engine oil, but not a synthetic, just a good quality oil. You should not need to keep topping up the gear box oil, unless you have a leak.
hope this helps.