I also have white fiberglass pool without tile. I am planning on a DIY tile job this fall. From what I've seen & heard it doesn't sound overly difficult.

A. You have to drain the pool below where you want to install the tile.

B. You use silicone to attach and grout the pool. Some people use regular silicone but I am considering using Marine silicone. http://www.hometownstores.com/detail.aspx?ID=84082

Here are a few DIY fiberglass install sites.

http://www.fiberglassswimmingpooltiling.com/
http://www.flextile.com/index.htm