Here is a diagram for you
If you look the power sorse goes to the switch first then dissreguard the netural coming into the light
Let me jump in and clarify if I can ..
On Glenns diagram .. where the light is shown remove the light and draw that wire straight thru .. that is your nuetral .. on the last 3 way switch take out that little verticle connector and you will have a hot from that switch and the nuetral that you carried thru all the switches .. thats where you connect the light
Yes just add another 4 way