You need a support block to hold the hammer with the pin able to fall into the block. Tou need, must have, a solid in punch to tap the pin out. A 4 to 8 ounce hammer.
Lay the hammer in the support block, which can be a chunk of hard wood or molded plastic. Use the punch and hard to tap the pin out. The pin is a tight fit. The short end leaves a depression to center your punch.
To put the pin back you might need a tool to hold the pin as you start it. Just tap it flush or just very slightly below the side.
Why didn't you send it to Ruger for repair and tune up?