Which camera should we get?

Chris and I are in the market for a really nice camera (you know those semi-pro ones that are easy to use for the common man). We had already decided to get one for when the baby comes, but since we go on a cruise (oh yes!) in a a week and a half, we want to get it before then.

So I need a crash course and lots of advice:

1. Which brand? Basically we heard either Nikon or Canon.
2. Which model? They are all numbers to us and mean nothing.
3. What are other things we want to make sure it can do?
4. Where would you buy it? We've heard of friends that buy them at some places and it comes with a training class.
5. And that's not all... so there are a million things you can get with it, what's necessary and what's not.

We've heard that they range $500-800ish dollars, so that's the price range we'd like to stay within.

I always appreciate all your good feedback!