it's pretty simple. The first thing you need to do is to remove the backplate of the engine. That starts with removing the ez-start assembly. That should be held on with 4 screws. Once that is off, then remove the backplate. That's either 4 phillips screws or 4 hex screws. Either way, remove them and the backplate will pop right off. You can now see the back of the crankshaft as well as the piston's connecting rod.
Next, remove the cooling head. Again it's either 4 phillips screws or hex screws. You reach those by coming down from the top of the engine. When you remove them, make sure you keep a close eye on the metal gaskets that go between the bottom of the head and the top of the sleeve. Don't lose them.
Once the head's off, you can get the sleeve off. It should just pull straight up out of the engine. It may take some coaxing, but it will come out. If it's too difficult, one strategy people will use is to put a thick piece of string or a heavy zip tie through the exhaust port and then try to turn the crankshaft. That'll pinch it in the port and then force the sleeve up. Pops right out after that.
Once you have the sleeve off, the piston will jump right out once you unhook the conrod from the crank. Take a moment to make sure you mark which side of the conrod is facing the back of the engine. That way you put it in correctly when you reassemble. Also take note of any features on the piston that might show you which direction to put that in, too. If it doesn't have any, then you can put it in either way.
To reassemble, just do this backward. Be very careful replacing the cooling head. Tighten the screws slowly and in a star pattern to minimize the chances of developing an air leak.
