#1
can anyone point me towards a good online tutorial(s) for cubase that deals with mixing and mastering a typical rock song IE drums, bass, guitars, vocals

I'm tired of my stuff not sounding right.
#2
The most important thing for mixing and mastering is having a good set of studio monitors. Why? Because they attempt to provide you with a flat-EQed, non-colored sound. Monitoring headphones are passable, though you may have issues with detecting sound width. One tip I've started to follow is adding a spectrum analyzer to the master track. This allows me to view the frequency range; most of the time you want it to be level.

Since I don't actually own Cubase you should start by looking through Youtube for detailed tutorials.