I have some experience in chassis building. First thing I would do is go to your local book store or amazon.com and pickup a book or two on the subject. Then decide if you have the tools/equipment/ability to see the project through.
You don't necessarily need a frame jig. I have built one on a heavy duty oak bench before I built my own jig out of 4x4 heavy wall tubing.
Some photos here. Good luck should you decide to continue.
