A Co2 pistol is a bit more annoying to maintain than a green gas one.
As BigStew said, you should remove the gas cartridge when not used. (This is a bit of a pain if not empty)
Yes as you said, use a lubrication cartridge every 10 or so. (Adding oil for each replacement as above is also very good)
Remember: Don't oil in the hop or barrel. They must stay dry.