If you're mechanically inclined, then you should have no problem doing this yourself. Go to www.mechbox.com
. They have videos of the disassembly of an M4 and mechbox. Your Dragon is just an M4 with extra cosmetic furniture on it.
Seriously, if you plan on getting into airsoft, you're going to have to learn to do this anyway. The mechbox does require occasional maintenance in terms of cleaning and lubrication anyway. Might as well learn how to do it yourself.