This involves the polishing of the action components to reduce friction, and possibly the replacement of one or more of the action springs. The sear angle may also be modified for a lighter trigger pull. A well done action job is money well spent. A poor one can ruin a good gun and or make it dangerous. Pick your gunsmith with care.
Blue Book of Gun Values will help.
Single action means the trigger only performs a single action; it drops the hammer to fire the gun. The hammer on a single action gun must be cocked before the gun can be fired.
you probably mean PPK or PPK/S which is a Walther hand gun in 22 cal, 32 cal or 380 cal.
you get what you pay for.
check under grips at: gunlist.com
Average what? Hand gun? Long Gun? Type of action? Single shot? Semi-Auto? Bolt Action? Broad answer - 5-100+
Generally speaking, a single action gun is a gun that has to be cocked before it can be fired. The term "single action" comes from the fact that the trigger only has a single function; it drops the hammer to fire the gun. A good example of a single action handgun is a 1911 style or a Browning Hi-Power. Also, the old style "cowboy" revolvers are single action.
Possibly a Colt Single-Action Army revolver, Serial No. 1, for $862,500.
pawn shop, gun shop, gun show
Gun shop, gun show, estate sale, garage sale, egunparts.com
100 or so
50 USD