Just to be clear: whichever changes you make it's ok, that's your work, you have every right to just change everything I've done with it ^^.
The "underground access word" is Sewers.
And I don't think a newcomer who was never played fallout before needs that extra bit of information ^^, but it's your call! (Having it like some secret for experienced players is nice, they'll learn about it sooner or later anyways, and that's the fun.)