The service manual. It isn't too hard as long as you have some mechanical know how. There are a few tricks I learned by doing it twice. First, you dont need to buy the tool for the timing chain tensioner. Just use a very small flat head screw driver and a pair of needle nose vice grips. Also I used a wire coat hanger to keep the timing gear and chain in the exact same spot so I didnt have to move it at all later.
I havent had a chance to ride my new setup yet. I was in a car accident and messed up my shoulder a bit so isnt that fun? Put a new build back together and not be able to ride it. I did start it up though and do the cam/piston break in. It sounded very nice and ran extremely well. I did the 11:1 so i could stay on premium fuel as some of the long trail systems in Wisconsin it is hard enough to get premium.
Also, watch the piston rings you get. They sent me the wrong spacer ring for between the oil rings. It was too big and I had to have them send me the right one. I bought mine on ebay as well.