Is the toilet a one piece toilet or a two piece?
And does the toilet inside look like that in the video?
1) Success - thank you for your support!
2) That video is exactly the part that needed to be replaced, though they made it a bit more complicated than the way I did it.
3) The issue (as explained by other videos online) is that the seal piece develops blisters over time, which allows water to get through. Anyone else experience this, and/or can recommend ways of just avoid the issue entirely (other than getting a different toilet)?