HB,
From the picture, it looks to me like the 1st step would be to remove the cap (part KK) off the rear of the action. It should unscrew. Careful so the spring behind it doesn't shoot out anywhere. Then the parts of the bolt should slide out through this opening once you unscrew the ****ing bolt (part HH).

The gun should have a tool for removing the nipple (LL/MM) on one end of the tool, and the larger end should be used for removing the breech plug itself. It should look like a long socket, probably several inches long, with a hole drilled through each end of it. Just take the nipple out, flip the bp wrench around and take the plug out.