On your bike, maybe a 5 or so. If you have not done it, get the manual here. I would think you just need to pull the tank. Remove the valve cover and you have access. From there, break the old chain and attach the new one to the old chain and pull it through. If the old one fell off though, you might want to make sure the tensioner is working right and the sprockets are ok.
The ride IS the adventure. The destination is just to get gas!