hey jules, I would suggest to start by reading a few of the informational threads located at the top of the forum. Here are the links:

http://talk.hairboutique.com/forum_posts.asp?TID=30347

http://talk.hairboutique.com/forum_posts.asp?TID=30346

Spend plenty of time researching the various methods and decide which is right for you. Ask tons of questions, the ladies here will jump in and answer any question you may have!

Yes you can buy hair and some extensions supplies at the beauty supply stores. But many of them dont carry some of the better brands/types of hair or much variety of extensions supplies. So I think most people are buying online from some of the various vendors.

Damage depends on a few things. If your hair is already in poor condtion extensions can add to breaking/damage. And if extensions arent applied properly or removed carefully that can also lead to damage. If the extensions are applied correctly and removed carefully they should cause little to no damage. Many people have grown their hair out successfully while using extensions, others claim that their hair is thinner or worse than before.

There are several methods that are simple enough for a DIYer to do, and if you have help thats even better! The LG (liquid gold) is easy enough to do, its a little messy as the glue can be stringy, but simple to do. Another easy method is using extended wear tape, like protac, supertape or also called by a few other names. This in my opinion is one of the simpliest methods for a first time DIYer. You can expect anywhere for 3-6 weeks average out of these methods, and it really just varies with the individual.

Synthetic hair is ok for some, in fact some people LOVE it while others absolutely hate it. I think its just an individual preference. Each have their pros/cons.

Hope that helps!