Please excuse my ignorance and stupidity, but it's late and I need help urgently.

I just got a Yamaha S90 ES a couple days ago, and I need to record a song on it for a party.
I need help in the following areas:

1. changing the tempo of the given drum rhythms ex. the first one performance mode, wide river. how would i go about changing the tempo of that.

2. recording that drum rhythm as a track, then recording layers of bass, guitar, organ, piano, etc on top of it, so that when i go back to it later i can just access it, press play, and watch it go.

If you don't have the time to explain all this to me, does anyone know of a site that really explains it in detail? Thanks a bunch.