Re: Hello, Im new to this forum and to motorized bicycling. Im from Syracuse NY
Welcome to the forum. We're glad you've joined us and hope we can help you with your firs project.
Your questions are little vague and would take pages to answer. "Anything I need to know" Would require posing much of what has been written here over the years. I would suggest you give our 'Search' a try. Simply type in a keyword or words and you'll have plenty read on every aspect of building, riding and maintaining a motorize bicycle.
As for your choice of where to buy an engine kit; we usually suggest to buy from a reputable vendor who will stand behind his product if there is a warranty issue. Some ebay sellers are here today and gone tomorrow. Buyer beware.
Good luck and have fun.
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"