I selected around the seat top with the Freehand selection tool set to Point to Point.  I was careful to select exactly around it.  Then I cut and pasted that as a new layer.  Going back to the background layer, I made sure that where the seat had been on the toilet that I filled it with white.  For the tank top, I copied and pasted as new selection until I had the tank top filled in.  I didn't worry about the part right behind the top of the seat, the wall, because it would be covered.  Most of the tank top itself would also be covered.  Ok.......so now I had some space between the top of the seat and the bottom of the seat.

I'm going to guess you went 10 rounds with the deform tool?  You will need to continue to practice with the deform tool in play mode rather than class mode.  The deform tool can become a very good friend to you in PSP.  But let's say that the right side was fine, but you couldn't get the left side to work out right.  Then you can use my cheat method.  First I used the Clone brush to touch up a few spot on the right side.  I also used the Draw Tool/Single Line/ Size 1/Antialias checked/Vector unchecked.  I used a dark brown to go along the edge of the right side to patch that up.  Then, the right side looked fine.  I used the Freehand select tool, once again using Point to Point.  As you can see in this closeup, I was careful again to just select the seat.  That is how I selected the seat top above.  Once selected, I copied it and pasted it as a new layer.