roof mount DVD

Has anyone added a roof mount entertainment system, either OEM or after market? My question is, are there little mounting tabs welded to the roof already or do you have to make holes in the roof? On another note, has anyone installed replacement sun visors with the DVD player (and LCD) in the passenger's side and a vanity mirror (and LCD) in the drivers side? ebay and the mp3 store have a wide variety of these items. I'm just thinking about it as yet but it looks very interesting. Especially if you can find a unit with 2 video inputs so a back up camera could be tossed into the mix as well. Any thoughts or suggestions appreciated.