Re: is it worth the potential trouble?
All of this boils down to your level of mechanical skills. Those of us who can fix anything do not hesitate to take on a challenge. However, if your skills are marginal, it's probably best that you mitigate some of the risk by starting with new, less problemmatic parts, both bike and engine. Plus, if you buy new, you can pick how the parts are configured instead of accepting what someone else decided on, important things like whether the frame is aluminum or steel, the type of brakes, quality of the wheels. All of these things are more important on a motorized bike than on a pedal bike because of the increased speed. You are wise to seek advice from this forum, these guys have "been there, done that" and there is great value in their experience. Read as many threads as you can before you start. It will save a lot of time and errors. Good luck and keep us posted.
"If bulls didn't have horns, everyone would be a Matador".