iPHone, number of emails, checking display

I'm getting ready to pull the trigger and go get an iPhone this evening. My nearest Apple store is about an hour away and I rather buy it there then from an AT&T store. Is it possible to check the display before I leave the store to verify I don't have major issues? I'd hate to get back home and then have to go back another day if it has a bunch of dead pixels, etc.

Also, how many voicemail messages are you allowed with AT&T with regular not enhanced voicemail? I'm wondering if this is limited to 15 or so or if it is different since they end up getting downloaded to the iPhone.

I'm still a little apprehensive with buying thinking an update is just around the corner but really can use the email, calendar and contact functions for work and don't want to wait much longer.