Start with a kit (Tamiya or Wedico)!!!! If you start trying too buy parts to assemble one, you'll just be disappointed with the finished product.
You have to be in the hobby for a couple of years before you actually know most of the suppliers that have parts available for us. The modifications for these trucks seem endless and the money that could be spent on a build by purchasing parts separately could cost you in the tens-of-thousands-of-dollars.
Starting with a kit will give you the basics and all you need to purchase to make it run is an ESC, a TX/RX system w/servo's, and a 7.2 volt battery with charger. The whole bundle should cost you somewhere between $650 - $1,100 depending on the truck you choose, the quality of radio, and the type of ESC you choose.
Happy building and Good luck
- RCT