Got it fixed guys.
A little PBlaster in the cylinder allowed me to rotate the piston using the flywheel. The cylinder seemed to be in great condition as far as I could tell there was no scoring whatsoever, but then again I don't exactly have a trained eye for that sort of thing.
I would say that it definitely seized due to not being used, because it was not hard to unseize at all once I put PBlaster in there.
Is there anything else I need to do to make sure everything is working properly?
Thanks for all your help guys!