thanks for the replies guys,
it stopped leaking oil since I've left the oil container under the seat half full.
I've been using a few drops of this bicycle chain lubricant to prevent any rust, lets see how it works out.
That stuff is actually pretty good stuff. I use it on my mountain bike chain. It sits outside all year and has no rust on the chain. But, it gets oiled before every use.
As for your bolts--
If the scoot is exposed to questionable weather on a regular basis (outside parking or rain riding), then bolts are going to get rust eventually. I would just keep some replacement bolts on hand and change them if they need it.
Stainless bolts are a good upgrade. They'll last a long time, but even stainless bolts WILL corrode over time. But the scooter will probably die before the stainless bolts do.