Yes, you can remove the crankshaft out of the block without removing the piston and rod, I do it all the time. Once you remove the rod cap from the rod, push the piston all the way up into the cylinder as far as it will go, then rotate the crank journal down and work the crankshaft out. You will have to remove the balancer weights.
You can pull out the top seal without any special tools, an awl or pick even a small screw driver and you can pry it out, however you will need a new one. It would be very difficult if not impossible to remove a seal without some damage.