sourwire wrote: "You are not allowed to change system configuration." I tried gksu services-admin from the terminal, same thing.
First, as Husse's signature says: "Don't break stuff if you can't fix it."

Messing around with things that you don't understand is not very wise ... A lesson you now fully understand I guess.
Criticism apart, the error you get sounds more like an authentication issue. Did you mess around with the root account too? Does stuff like
sudo su - give you a root shell? Besides, it would help if you could be more precise on what
exactly you did to your system.
I don't know about others, but I for myself
make notes on paper in a 'log book' before I do something potentially stupid (yes, I too do very stupid things sometimes!). On that paper I write down
- the time and date
- what I intend to do (e.g. disable "gdm")
- why I intend to do it (e.g. "machine is a server, no GUI needed")
- and how I did it (e.g. "removed relevant symlink from /etc/rc*.d sub-dirs")
If anything goes wrong I can easily revert my steps. You might wish to do this as well in the future? Even if you can't revert your steps yourself, you can then at least tell others what precisely you did and why you thought you had to do it. This helps a great deal to understand the causes of the problem.
Unprecise descriptions such as "I disabled some services and now my system don't work" doesn't really help to find a solution for you.