Re: greetings from new orleans...
Welcome to the forum mrfoochie (from a newbie). And to the obsession. Whatever you build, it's sure to be loads of fun to build, aside from the inherent challenges, and fun to ride! Challenges come from the fact that these are bicycles, after all, and bicycles aren't built for motors. Although the Chinese engine kits are built for bicycles, it's not always a perfect fit, but ususally a workable fit.
A motorized bicycle won't match the soft ride of your Vespa, so figure on buying a comfortable seat for your bike (I'm still looking for the perfect seat).
The fun factor is really hard to put a value on for me. I retired from work a few months ago, built my bike in early April, and average 20-35 miles a day on the bike, "just 'cause", for no other reason than the ride itself. I call it my reward system for knocking things off the "honey do" list, and being an all-around good guy.
Hope your build and ride is fun, too.