Put a split sec. of silence in the system greeting. As for the prompts turn off any that you don't want, do it on user 1 and assign user 1 to the A/A and custom messages.
what happened to the original installer?
All that you want to do is very simple but it sounds as though you may be in over your head.
May be time to call a certified Tech. and have him set it up the way you want it and explain
to you as he's doing it.