1) Scale-Wiki is great for how-to's, as is this forum.
2) Alot of us buy our kits from Hobby Town USA or Hobby Link Japan,
http://www.hlj.com/
3)Fujimi makes a 3rd Gen RX-7. It's stock body, but no engine detail.
4)You'll need model glue, razor blades, tweezers, sprue cutters, paint brushes, paints, spray paints, paint thinner, and alot of other stuff if you want to get into more detailed building.
5)Start with a pretty simple kit. Revell is an okay place to start. They have some good models that go together very easily and look decent.
It takes time and practice, but it's very enjoyable and stress relieving...unless you are Scale-Master in his "scale" Super 7 build.