FWIW...I had mine seize on me...Being the cheapskate I am, I decided to take it apart and see why, as it was just sitting around and seized....Anyway it fairly easy to disassemble...There's 4 plastic wipers that act as the air pump mechanism...I found all kinds of crud on the walls, oxidation actually....Cleaned all that crud off, cleaned up the wipers, douched it with WD40...put it back together and it ran the balls again...
Worth a shot if your into that kinda stuff....
Remove the front bolts to get the pulley off....I think there screws behind that to undo the case to get at the guts...It was awhile ago, but fairly straight forward to disassy/reassy...might just save your self a few bucks !!!