I assume you're talking about RAID 0. Answers:
1) Little impact on gaming. Your loading times will improve a bit, but not much. You can improve your gaming experience investing in more RAM (get at least 4Gb-6Gb, depending on your system, plus Windows 64).
2) You need 2 identical HDs and a mobo with RAID. Most mobos have RAID today, though.
3) Read the manual of your mobo. You'll find everything there.