Yes, it's normal for an LCD to have dead pixels on arrival, and no, they don't usually lead to more dead pixels.

There is a minimum number of dead pixels for replacement... something like 10 over the display, or 5 within a certain area. But if you're in the guarantee period, you can return your notebook for any reason, so usually they'll replace the display for any number of dead pixels within that period. However, you may end up getting a display with 3 dead pixels, so it's up to you whether you want to go that route.

My notebook has a dead pixel, and while it does bother me a little on occasion, it hasn't impaired my enjoyment of my computer - I don't do graphics work or anything that requires that kind of precision where all of millions of pixels must be displaying perfectly.