I'd do it. It's not rocket science, if you look at the complication threads in the fill area, the trained professionals can jack up a port or tubing just as easy. I submit that you would be even more careful since it's your own belly you're poking. I have thought about it myself, I'm not banded yet of course but I did think about it. The only reason I wouldn't is I wouldn't want to risk insurance turning me down to repair it if I did mess it up, but then again who can say who messed it up and when. For the average joe, maybe not the best idea but knowing what I know (former medic) I wouldn't hesitate at least to do an emergency unfill.
And as far as getting the needles, you can buy them directly from the manufacturer, obviously the OP is not gonna buy them at a garage sale or off the street, so the safety/efficacy of the needles shouldn't be an issue.