Sunny G makes a great point. Although it will be very useful to learn how all the parts are modeled at this stage you want to use the supplied parts as noted by Sunny G. All the chassis parts are supplied in the 2013 KOP under the Drive Base Kit.
A very cool set of videos on how to use Frame Generator is available in the the Built By Design series. Here is the link to the Frame Generator section.
http://students.autodesk.com/?nd=first_inventor
It is the sixth video in the list.