Its not all that hard, but then most of my life i have worked in construction/engineering and have no issues with using tools and such. I would use a micro router to do all the cutting, start my making a cutting jig for all the external cuts, you really need these cuts to be perfect and straight to keep the car balanced, then after you have cut the chassis, you can clamp the old one on top of the new one and use it as your jig to drill all screw holes and then route any other internal cuts that need to be made. All up it is not hard to make a copy of chassis using aluminum, carbon or glass fiber, you just need to take your time with it and get your initial setup jig perfect.