Gear oil , use automatic transmission fluid, 1200ml. On the sump there is an alan key sump plug to drain ( do not touch the 17mm hex beside it, you will regret it if you do) Neutral is never easy to find on this model, but easier with TQF.
50 : 1 - any quality 2stroke.
Decompression levers available from motoswm. Probably get a replacement seat cover there too.
SWM's won a world championship, and the ssdt. Very capable bikes.