jmbones,
You can't actually get just the bearing, you have to buy the entire hub assembly.
I strongly recommend using OEM Nissan wheel hub assembly part # 40202-JG01A (same # for both sides). They are ~$145, not much more than aftermarket parts and should be of much higher quality. Also note that the Nissan part comes with new wheel studs pre-installed.
BTW, before you go off and replace a bearing, make sure the splash shield behind the brake rotor is not rubbing. I recently had to bend mine back as it was contacting the rotor making rubbing/scraping noises! Usually bearing failure makes more of a groaning noise.
