Wouldn't the most important step be identifying the source of the oil? Otherwise, how do you know that you won't be right back at square one after cleaning/replacing it? Are you positive its not power steering fluid that leaked onto it? That's a very common issue on SC400s.
Im sure that it is power steering fluid as I have not had to add any other fluids in 5 yrs of owning car. I know its a common issue and I plan to change out the serpentine asap. Whats best band to buy and can the alternator just be cleaned up once the leak is fixed?
That's good then. I don't really know the answer to either question -- I would hazard a guess that your alternator will be okay once dried out, if it isn't currently showing problems from getting soaked -- but I've always heard good things about Gates belts. And OEM is always a safe bet, of course. I would go with OEM unless the alternatives are significantly cheaper.