Go synthetic. I use Mobil 1. It may or may not really be better, but I think there is probably some benifit to it. I think 5k intervals will be fine, I've been doing 3k, but I think that I'm going to change to 5k from the evidence I've seen. And use a good filter. I use K&N, it's a costly one, but I really think it is at least a little better than most others, so I shell out a few bucks more each oil change quite willingly.
