Do those small black and white tv's work? How much power? How do you
power
one? Battery?

20" Sharp Aquos, 12vDC. DVD player with it's audio looped into the Clarion
head unit. Video out goes to the TV and the Raymarine E-80 chartplotter.
Video on the chartplotter is basically pointless on our particular setup but
I connected it "because I could". The audio looped to the radio really
improves watching movies. MUCH better sound than the speakers on the TV
itself.

While I have your attention :: how much power does a laptop take up?

It varies quite a bit between different laptops. There are also different
ways to power them. You can either use an inverter and the normal power
brick, or get one designed to run off 12vDC. The latter generally consume
less wattage, and are also usually quite a bit smaller/lighter than the
regular AC power brick.

Also, how long will a laptop run before it is out of juice?

My ancient 1ghz Toshiba runs about 2 hours, but the wife's tiny little Sony
gets 8 hours.