Coolmods aren't really guaranteed to fit as i bought a full case with buttons and of the screw holes was smaller than the screw itself, thus making my WiFi support to be loose, i haven't seen the ones from DX, but from what iv'e seen and heard they are good, also on the coolmods UMD door, if u look closely on ur original, inside where the hinge for the door is at, the door would have to be forced closed rather than the original push and that's it, this door would have to be pushed then slid towards the hinge for it to lock into place.
there's my 2 cents