That's a short question that takes a LONG answer. ;-)
Yes you would need a power source for any preamp.
Here's an old thread that discusses how to power your preamp.
As long as you don't have any very strong signals in your area, it's worth experimenting with an antenna mounted amplifier.
As for what to get, well that can go from around $20 or so to well over hundreds of dollars.
Here's a link to a cheap experiment.
While the noise figure of that amplifier isn't the best, I've used to to show some friends locally what a preamp can do for them.
This is another view of a similar setup with approximate prices etc.
Mount the amplifier at the antenna and leave out the splitter if you don't need it.
And .... Here are some of my 'spare' amplifiers.
And another thread about getting power to your preamp.