if you can find the leak,
open the fill plug
drain the remaining oil
use marine plastic epoxy to fix the hole / crack... use acetone to clean off ALL traces of the oil first...
refil with light machine oil....
make sure that you get all of the bubbles out, unless you want errors.. tip, flex the housing in until the bubbles are gone, and submerge the housing in the oil and allow it to suck oil back in....
when full replace the plug.... and acetone / epoxy it back in place if you feel the need
I did this to a compass recently with no probs...
regarding the naysayers... I agree it's important.. but if it is done right there will be no problems... the most important bit is to get ALL the air out! b/c air compresses obviously and oil does not (well any more than water but we won't go there)