The first thing to do is to be sure of what your plan is.  How are you going to use the living quarters.  When I did my camper, I got some big cardboard boxes and made my cabinets, closet, Etc.  I then located, to size, the microwave, sink, Etc.  This allowed me and my wife to get a feel for what it would resemble when completed.  Cardboard and packing tape are easy to change.  Visit my web site for the complete process.  http://home.earthlink.net/~dheismann/

I hope that this helps

Good luck, let me know if you have any questions.

Turfa