HI,
Here are the insides of a DPFE. YOu will have to drill out the rivets and thread (tap) the holes for an 8/32 fillister head screw to put it back together...or re-rivet it. If it's a plastic one...I don't know...be careful when splitting the case. There doesn't apear to be much to "clean"...the one in the photo had about 35k on it.
DPFE insides Good luck,
...Ed