lots of options out there! easiest start would be a 2 stroke kit and you could be up and running in a few hours. Look around the site here and ask as many questions as you need to! there are a BUNCH of very helpfull and smart people here. Welcome!
i have not YET done a 4 stroke build myself. I do believe from what I have seen that they are a little bit more involved to build but I am sure that you could make it thru with help you would find here. I have heard that they are much more reliable and quiet!