[techie610]

First, welcome to the Forums.
What brand bike did you get?

Scoots do not absolutely need to have an exhaust gasket to run.
Any nut that will fit the threads will work. While your running it down, drop some lock tight on it, to secure it.
Either Gasket will fit, though. I use the full sized, metal coated on my bikes.
The welds on almost everything stock is crap. If the flange isn't 90* to the exhaust port, you will blow the gasket.
As long as the holes from the engine and into the exhaust pipe line up, with nothing in the way, you should be fine