The curb top should be sloped back towards the shower. Most door installations (if they use a bottom track) only tell you to caulk the outer edge. I put a Century door in my mother's shower and was impressed with the quality - I felt it was much nicer than the Kohler door I put on my tub. No extensive experience so can't help any more.
Installation often isn't all that tough. You will likely need a diamond core drill bit, but those can be had from Lowes or other suppliers.
If the opening is not plumb, then it becomes much more difficult and a custom door and install may be required.