Probably the easiest 'upgrade' I've ever done on the boat.
If you have an old Sealand (Dometic) vacuflush system and would like to upgrade to a more modern bowl/seat (more elongated) I can't say DO IT more strongly. Aside from the better seat dimensions, we wanted a 'cleaner/smoother to the touch' look & feel too since both the bowl and seat were an 'off' brown (not the bone color they should have been) color and rough to the touch from some type of cleaning agent the PO had used to clean them
Initially, working with the local Dometic guys, I was frustrated because all he would 'push' was getting a new Dometic 500 series toile to replace the original small/round bowl/seat. WRONG, I just wanted a new bowl. Since it wasn't something they carried, I grew tired of the 'push' and did a little research and found a great recommendation to visit Seacoast Services. After a quick conversation with George, I had two of their 5000 Series Bowls, and all new seals on the way.
Instructions came with both the bowls and seal (pretty much the exact same procedure listed) and each bowl was replaced, and re-tested, in less than half and hour.