Picked up an old Craftsman 10hp, 30" rear-engine with a sticky shift lever.  Seller was able to get it into forward gears with effort, so I know tranny works.  Got it home and shift lever won't budge from neutral.  I'm not much of a mechanic, so I'm not sure where to go from here.  I assume I need to get it up on blocks.  Do I need to drop the mower deck to get access to the linkage?  Do I then just follow the linkage to look for what is hanging it up?