I had to rebuild the lift on my 2240 about a year or so ago, when it started leaking down, chattering, and otherwise acting up on me. I replaced the two spool valves, the "O" ring on the piston, and a handfull of other seals common to the valve assy.
I described the symptoms to my buddy at the JD dealer, and he fixed me up with the parts. The only trickey part of the job was getting the piston back into the lift cylinder - the OEM "O" ring had been superceeded by a teflon ring that was a real bugger to compress enough to get back into the hole. The entire job took around 6 hours, and the lift has been functioning just fine ever since. I replaced the spool valve and so forth at the recommendation of my dealer mechanic, but after inspecting the old parts, I suspect I could have gotten by with only replaceing the "O" ring on the piston. All of the parts fit into one of those small lunch bag sized JD parts bags, but they cost me somewhere in the nieghborhood of three hundred bucks.