Don't buy from an online vendor if you're not comfortable wrenching your own bike. Seriously. Go find a bike shop, talk with the cats there, try to build up any relationship with them that begins with you spending money for their services. Learn what you like, don't like, recommendations and other things from people in real life. Then, and only then, if you feel like you might have it under control, go ahead and buy a bike online with the knowledge that if you get in over your head you aren't approaching a bike shop saying "Hi, I wanted to squeeze you out of business - fix this."

I have a lot of respect for those people who are offering great services, parts or even complete bikes online, but its just sad going in and talking with my friends at the LBS and watching them charge $85+ to build a BD bike for someone who would have gotten a better deal and camaraderie from going in initially and working with the local shop