There are 6 cylinders, 3 on each side. I assume you're talking about either the main lift cylinder (pushes the entire top up) or the bow cylinder (pushes the top out to the windshield) since the storage top cylinders are in the trunk.
The bow cylinders shouldn't take more than 1-2 hours to replace as they are accessible just by lifting the top up.
The main lift cylinders require removing the entire top from the vehicle, which requires removing the rear interior to get at the last nut and electrical connections.
My drivers side main lift cylinder is leaking, I also noticed a puddle behind my drivers door. I plan on removing the soft top one weekend to pull the cylinders, then reinstalling the soft top while waiting for the cylinders to be rebuilt. I'm going to have both main lift cylinders rebuilt, yet only one is leaking. For $600 you could have all 6 cylinders rebuilt.