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.
Pre-Amps: Local powering versus Remote powering
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.
Mini-Circuits ZFL-1000LN 15v Amplifier & ZFSC-4-1 4 Way Splitter question
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.
So I bought this Antennacraft ST2 "Scantenna"
And .... Here are some of my 'spare' amplifiers.
And another thread about getting power to your preamp.
800 Meg preamp