Quick question about replacements

So I am getting my 3g replaced, and I'm not sure how Apple goes about doing this. I've got the light leak problem and dust did appear underneath the glass. They said they had no replacements in stock, but when I checked availability, they had 16 gig whites in stock. Do they not open the box and give you a new one straight up, or do they have an actual replacement stock?

It's a brand new phone with manufacturing defects, and to replace it with a refurb is not what I expected. I don't even know if they have refurbs for the 3g yet, but I'm just asking. Should I call and tell them that I want a new one? I'm leaving for Vancouver next Tuesday, and the guy said it would be in then at the latest - and I'd like to get it done by then. Anyone know what Apple actually is doing for these replacements?