Not sure about the model number you provided but I do know that the Kwikee 3000 jacks on our rig (pn 3700710) are not rebuildable, at least not easily..
I have read a time or two that they can be rebuilt. But they have to be cut open, rebuilt, then welded back together. Not something most of us can handle ourselves.
Replaced all four of ours when they started leaking one by one over about a years time. Removal and replacement is straightforward and fairly easy.
03 Itasca Sunova, Workhorse P32 with the 8.1 and 4L85-E