top end rebuild:
Pull plastic, pipes, gas tank, carbs, coolant hoses.
unbolt the head from the #10-#1 in that order, unbolt the cylinders and usually you'll need a rubber mallet to break them loose and pull them off
put rags in bottom end so stuff doesnt fall in, pull the circlips, pull the pins, pull the pistons off.
Take the cylinders to a machine shop and see what they need to be bored out to 64 mm is stock, order the top end kit (150 bucks including wrist pin to your door from a few places), and then take the kit and the cylinders to the machinist to bore them to the pistons themselves.
Install new pistons (facing the right way), install new pins, bearings, circlips, put cylinders on, torque them to 20 lbs in 3 increments (10,15,20), put the head on and torque bolts from 1-10 in order in same increments to 20 lbs and install all the rest of the stuff)
Then you get to learn about heat cycles and breaking it in
It's pretty simple, and not including the machine shop time and ordering and such it can be done in an hour or two.
I've actually done it in a half hour, its always nice to have a backup set of cylinders.