I hope to not have to do this to my thumper for a long time since it is new, but I did have to change a stretched chain in my Suzuki Z400 sport quad after only a season and a half. And that is a single piston engine/tranny just like our thumpers, so it may be very similar. My advice from that:
1. Have a shop manual or Clymer. My Suzuki Z400 FACTORY shop manual has so many pictures and was so clear you'd think it wasn't made for mechanics. I've ordered one because of that.
2. Mark the position of EVERYTHING YOU CAN. Just in case things get moved around. Set everything at TDC at the beginning, then you'll know where to get back to. My manual showed how the cams were set at TDC, so I didn't have to rely on my marks as much.
3. Leave lots of time. Don't expect to get it done the same day you start. Assume you will need gaskets. Take your time. If you have a friend who wants to learn, a second hand and eyes are always nice.
4. If you have access to a digital camera, take a ton of pictures. This has saved my buttocks more than once. And take notes, don't assume you can remember ANYTHING. BE ANAL

5. If you get overwhelmed, put it back together and have someone else do it. But I doubt that will be the case if you are careful.