Make sure EVERYTHING works before you leave the lot. Easier to get it fixed before you leave than afterwards.
I did a PDI on my current unit prior to picking it up. Then took another 3 hours on the day of pickup to make sure everything was corrected. Check everything, including DVD players. That was the only thing I missed on the initial PDI, found a bad AB switch, but let them slide on it, they sent me a new one within a week.
Aaron