Invisible login screen and getting very confused about gdm

[Zarastro]

Hi,

i'm still pretty new to Linux so commands about how to do stuff are very welcome when and if you choose to help me :-)

The whole story is this:

I had succeeded in installing FC 7 in dual boot with my windows installation. Everything worked untill the (i gues) 3th startup my colors of the graphical interface went screwy. Blue became red and stuff. I tried to change my graphic settings from within the Xwin environment but screwed everything up. The result was that I didn't see graphical interfaces at all anymore.

This made me startup a few times to a black screen. I knew that linux was still running so I tried all kinds of key-combinations to get it to go down again. That worked but I hit my keyboard quite hard :-p and I'm guessing this is when I broke stuff.
After a few reboots I finally found out where the '3' for setting the runlevel at boot goes (the first line of the boot command, not the second) and I was able to boot to text mode.
I reconfigured my X server so my desktop is working again.

The problem I still have is an invisible graphical login screen. When i boot in textmode, login and startX there is no problem but the login screen that you should in a normal boot is invisible. The booting screen that you get before (where you can choose to see the details of the boot) works fine.

I read on this forums about having to re-setup your gdm but when I try

gdmsetup

I get : The gnome display manager is not running.

When I try to start gdm from

/etc/init.d/gdm start

I get the message

bash: gdm: command not found

Then i figured: I'll just set my runlevel to 5, that should get gmd running but both init and telinit are not recognized.

So my 3 questions are:
How do I get my gdm to run?
How come my desktop works fine when gdm is not running?
how can I set my runlevel or why dn't init and telinit work?

Thanks in advance