Its a 20 minute job.
The only tricky(ish) part is you will need to cut a length of round bar the same diameter as the attachment bolts and the same length as the draw tube. I used a piece of wooden dowelling I had lying around.
1) Undo the 2 bolts securing the hitch and remove.
2) Undo and remove the bolt at the back of the draw tube, you can usually reach it from underneath the A frame
3) Pull the old damper out and feed the new one in
4) Replace the back bolt and tighten
5) Push the end of the damper until the holes lines up and push in your "dowel"
6) Replace the hitch and push the front bolt in, then push the rear bolt in, it will push your dowel out
7) Tighten all bolts
8) Make a brew, sit down and admire your work
To get the right damper you need the ETI number form the hitch head, remove the frame cover and stamped on the top of the A frame you should find a number such as ETI 811011 that is the identifier for the damper