I've had a few of the Vax cylinders apart and yea, the wheels have to come off usually. It's horrible as the plastic is really brittle and cheap. If you can peer into it and see where the locking tabs are and start there you might be alright, also if you can bend back the wheel enough to get the screws out, removing the wheels may be less brutal once apart...
But then again the wheels may not come apart, so don't mega hoof on it...