I have some hammers and triggers that I covet like gold, however, if you can identify the exact problem I might be able to help with parts.
If the hammer stops have been filed, both the hammer and trigger are beyond the point of no return, means you need to replace them both.
Don't fiddle with it if you don't know what to do or you do not have the proper hollow ground screwdriver blades or tools (e.g. a pin pusher) and especially NOT if your patience gets exhausted quickly.
HOWEVER, if you feel confident of your abilities, remove the side plate, clean the inside as Mike Maher stated, only difference is the sidle plate is removed now so you'll be better able to spray down and clean the "innards".
Do not remove the sideplate if you don't know how. Do not remove the side plate before you ask for instructions. DO NOT PRY THE SIDEPLATE OFF ... NOT EVER !!
