I've done several DIP triggers/guards on my rifles...latest was the Pink one for my Wifey's Marlin 60...
But FIRST, before doing anything else...clean the bejeebers out of it.
Remove from rifle.
Totally dissassemble it, removing all pins and springs, and the trigger itself.
Clean it with pipe cleaners & q-tips...and a toothbrush if needed.
Polish the front of the "P" portion of the trigger...
Re-assemble in reverse of how you took it apart.
NOTE: those pins can get hardcore stuck, I've had to soak overnight in WD-40 to get 'em out...
the older they are, the more rust & grit accumulate in the pins...
if you don't have a proper punch set, this would be the time to go to Harbor Freight and get one...lol
Why I love DIP trigger guards & triggers...
1. They are aluminium. Unlike the plastic or pot metal ones that the MFR provided, will not break, melt, or otherwise crumble.
2. They have threaded screw-pins, unlike the punch-pins you just took out, are EASY to remove & replace for cleaning.
3. "P" adjustment screw removes disconnecter pre-travel, also utilizes a smaller contact surface for less drag.
4. Overtravel screw reduces...overtravel.
5. 3/8" wide trigger gives better finger contact and better fulcrum angle for an easier trigger pull.
6. Add in lighter springs (homemade or MCARBO) for an even better feel!!
I've polished enough old rusty Marlins to get to the point where I'd rather buy the trigger/guard combo...its worth every penny