Whether or not "upgrading" to 2.0 is a feature of your motherboard is irrelevant - like I said, even if you install a 2.0 card it won't saturate a 1.0 slot's bandwidth. Either way... take a look in your motherboard manual (which can be found on the manufacturer's website, if you don't have a physical copy).
To figure out the power requirements of a video card, check out its manufacturer's website, or run a Google search (e.g. GeForce 8800GT power requirements). I'm sure you'll get more than enough information - otherwise, feel free to post the card here.