I have just recently purchased and built a new computer, and I installed redhat 9 not finding the option to boot into "text mode" instead of gnome. I will eventually be putting a different window manager on as well i think.

My question is: is it possible to add some lines to grub to allow me to choose to boot to text, gnome and/or some other window manager?

grub doesn't handle either of the issues you describe

To boot into text mode
As root, edit the file /etc/inittab

Change the line

id:5:initdefault:

to

id:3:initdefault:

To add window managers to the graphical login screen

Create a file with the window managers name in /etc/X11/gdm/Sessions with the following lines

#!/bin/bash
exec /etc/X11/xdm/Xsession window_manager

For example, to add fluxbox:

vim /etc/X11/gdm/Sessions/Fluxbox

and put in it:

#!/bin/bash
exec /etc/X11/xdm/Xsession fluxbox

If you are going to boot into text mode create a file in your home directory named .xinitrc and add the line
exec name_of_window_manager

Then run the command startx.

grub doesn't handle window managers...it's purpose is to help you choose which kernel to boot.
You're booting into gnome automatically because many distros are designed with the assumption that people want it that way, so they start up X without asking, and then use a session manager or just load up the default window manager.

If you want text mode, look into /etc/inittab. This file contains the line
id:5:initdefault:
change it to id:3:initdefault: and you'll start in text mode.

edit:
Hi...my name is mikshaw and I like to post things immmediately after someone else just said the exact same thing....

I'm glad it happens to other people beside me

Actually if you want to choose at boot what runlevel to start into you can pass it as a kernel (actually init) parameter: so you may add your grub entry such as:
here is where i found it:
http://216.239.59.104/search?q=cache...hl=en&ie=UTF-8