you are going to have to split the cases, it is not that hard just keep track of all the parts you have to remove first. when you split the cases the trans will be open and the shims and thrust washers will need to be kept in place on the shafts. if you do not have a service manuel get one! You will most likely need to replace the crank bearings. As far as the wrist pin soak it in PB Blaster and try heating the piston and rod, you can use a bolt that will fit inside the wrist pin and a larger socket on the other side with a nut to pull the wrist pin into the socket. this method will put no side load on the rod and the least amount of damage. HMMMMMMMM things you should do get a rad valve, have the porting cleaned up and rejet, you will be shocked how much power you will get and how wide the power band is. if you ride woods try a flywheel weight around 12oz works well. if you want even more hit fmf fatty and shorty silencer. be prepared the jetting will be way off on the main!