I found the job to be easy and the two I had to do did not take too long at all. I bought the tubes flared on one end and the tool. I got the old ones out easy with a hammer and old chisel. I thought I bought the tubes the right length and extra long ones just in case, but I ended up having to use the long ones and cut them with a large pipe cutter (local hardware store). I am pretty sure I cut them 1/4" longer and loaded up the inside with 5200. I might regret that if I ever have to do them again, but now I figure if they crack and I don't see until after the season the 5200 should provides protection. Have some paint thinner, or mineral spirts on hand to clean up the 5200 if you go that route.
My old Offshore I bought the tubes from Gemlux. I was going to do that again but at the time they didn't look available. At the end I thought the brass tubes were much easier to do if you buy the tool.