Replacing the top-end is fairly simple if you follow the directions in the manual. Once you have everything apart, make sure to service the powervalve assembly and deglaze the cylinder. Measure the ring end-gap before installing the piston and rings, if the gap is too small serious engine damage can result.
The Weisco piston is an excellent choice ( I use them exclusively), but you must be sure to break it in properly and carefully, or you will be rebuilding it again due to seizing it. The Weisco is a forged piston, and is very sensitive to proper break-in. Did I say break it in carefully? I can't stress that enough.
You definitely need a good torque wrench to do the job properly.