If you can see the pistons, you got the head off OK. If your problem is the valves, you don't have to go any further. If it's the rings, you really need the manual to do everything correctly. But generally, the block comes off the pistons still connected to the crank. The hard part is slipping the block back over four pistons and rings. It helps to have extra hands holding the cam chain and the pistons and the block. There's usually a lot of "lead-in" on the bottom of the block to get the piston/rings inside, but Yamaha may have a special ring compressor to make the job easy. If you break a ring, it all has to be done over again. Good luck.