Will installing/ running Bootcamp on my Mac require reinstalling OS X?
Boot Camp creates a separate partition on your hard drive through "non-destructive partitioning", that is, by taking a chunk out of the free space left on your hard drive. You should always make a backup first, just in case, but the expected result is that you will simply end up with two partitions instead of one on your hard drive. One will be for Boot Camp, and the other will be for Mac OS X and all of your existing files/applications/etc.

See this Apple support document. Also when you start Boot Camp Assistant it will present a guide that you can print out to follow along with while setting it up.