You got yourself a lazy locksmith
I spend about 40 minutes swapping the pins over this evening with good results. I've never attempted lock work before, but I like to tinker.
Here's a description:
From the back side, with the lock open, depress the spring loaded tab with a small, thing screwdriver and push the cylinder out of the front side of the housing. On the tank compartment, it helps to have the lock off the lid, and the rubber cap and cosmetic plastic ring off first. The plastic ring will prevent the lock from coming out of the housing.
Remove the key, and then pry up/ out the 2 crimps on either side of the face of the lock. Be careful not to mar the edges of the face too much, as it fits snugly into the housing collar and needs to both fit back in and rotate in the shoulder of the lock housing.
Use care when removing the face of the lock as there are 2 springs holding the red key-hole cover closed. These are NOT captive springs.
Under that cover is a brass pin that retains all of the pins and their respective springs (also not captive). Insert the key to retain all pins and springs, then tap the lock face down to free the retaining pin.
Holding cylinder in an orientation with the pins facing up, cover them with your finger and remove the key. If you don't hold them down, they may spring out. Keeping the orientation of the pin slots facing up, use tweezers to remove each pin, keeping track of their order.
Reassemble in reverse order, placing new pins in each slot, then replace the retaining pin, then the key-hole cover. Use a pin drift or punch and a hammer to crimp the face back on to the housing. Be sure the slot is oriented precisely. I hit mine at a 45 degree angle to start the bend, and a second strike straight down to tighten the fit. It worked very well. If your face was bent or flared out during removal, re-shape the edge with careful hammer work.
This shows the pins out of the first cylinder, and the difference between the cylinder with the cam for the helmet lock (2014), and the one with the screw mount for locking tab (locking tank).