Maybe it's best to leave it together... lower quality guns don't like being taken apart, as they often use self-tapering screws.
Are you having any specific performance problems? If not, sometimes it's best to wait until it breaks before taking it apart and upgrading.
If you're just looking for general performance, then maybe a new battery and charger would be your best bet to squeeze out a bit more ROF and better trigger response. A new barrel and hopup rubber for a bit more accuracy, if necessary...
If you want lasers, flashlights, or red-dots, then you can just mount them on without taking it apart.