First airliner. Questions.

All the airliners I've done, I've used the decals for the cabin windows, even the cockpit windows too

In that scale the decal windows look quite good.  As an alternative, you can use one of those vinyl "glue-like" materials such as microglaze.  You put a drop in the window opening with a toothpick, drag it around the opening to make sure a film covers the whole opening, and it then dries in a transparent film.  You have to do this after painting- no way you can mask over that stuff.

So decals is the way to go huh? Has anyone done anything else as far as windows goes?

I have a little Fokker 100 I'm using Dons for but using Testors clear window cement to fill the windows.  Not too many windows here.  With windows you can see into, I paint the inside a real dark grey or black.  For a bigger  Revell 747 I have I'm using decals with windows so I'll but something inside to block the openings with, fill the windows with putty from the outside, then sand smooth.  Chris