I'll try to explain better (it kind of confuses me too!)...the bottom rail has the first guide (at the top of the pic) for the wall. The guide below that is for the snap in section for the cove(which I believe is a type of rubber). However...the bottom rail is also a section of the cove. At the side opposite the guides it starts out narrow and gets increasingly wider as it gets to the guides. It makes a slope from the inside to the outside, like you would do with a sand cove. Does that make more sense? I'm sort of having a hard time explaining it.
The piece that snaps into it is shaped more like a foam cove, only smaller, and made of rubber. The way they fit together makes about a gradual curve as possible, so I would think nothing else is necessary.
Now, as far as site prep...under the liner I only plan on using sand. I know the ground is very solid, but since there has been a shed there for 20 years, I'm not sure about drainage. From what I can tell, there won't be much work leveling the site, so I can do it myself. Since I live in the boonies, no one has anything like crusher run here. The closest I could get it would be 60-70 miles away, and for how much they want, I'll put the pool directly on the ground before I pay that much. It's THAT bad. When I say 'nothing like crusher run' I mean only sand around here. Ridiculous, isn't it?
Thanks for the help, if you have any more advice to offer, I'd appreciate it.