Years ago my church did the same thing: the laptop motherboard crapped out in three years from all the hooking/unhooking of the VGA cable from the rear display jack. I understand that church money is only available almost never so buy durable and expect to use for at least five years. I recommend a desktop: for the same money you can get more everything. Also try to buy an outboard DVD player as well-- it's easier to do the invisible switching between sources. DVD on laptop is still crappy IMO, plus you don't want your 'underwear' showing when trying to cue up a fat powerpoint show and a DVD clip from the same video source.
Heard of this guy? Good tech advice
http://www.churchsoundcheck.com/ Mostly audio oriented but more video advice all the time.
With laptops you get the convenience of portability but that is the curse as well. Everything is smaller and flimsier with so much wasted engineering to make it all fit in an envelope. Buy a big box brimming with AV luxury for the same money.