Just take some mineral spirits and 0000 steel wool and scrub the stock down real good, wipe it down good with an old towel to mop up the crud, do the same thing on the metal with WD-40, then wipe the whole gun down with Formby's Tung Oil/Satin.

It will retain enough patina to look correct, rather than a garishly obvious redo.
JR


Be strong, be of good courage.
God bless America, long live the Republic.