When you run iwconfig (may need to be root), what do you get?
Make sure ESSID and Encryption Key are off and you're nickname (hostname) is set correctly if it needs to be.
A strange thing I've noticed is that I can NEVER get my IP by running dhclient eth1, which annoys me as I dislike the wizard I need to use to connect to the network. (It's drakconnect for mandrake, I think it's "redhat-config-network" for redhat, but I can't be sure as I haven't really used redhat for more than a few hours). That should be a GUI anyway, so as you're "not very familiar with the terminal commands". Now that wizard should take care of those errors you mentioned in the first post. If it doesn't, you'll need to run iwconfig. I won't go into the details of that when there's a good man page
Find out if the LAN you're trying to connect to does anything non-default.
If it still doesn't work I'll try to help, but I'm sorry if I'm just telling you things you already know. We're vastly approaching the end of my (limited) knowledge and experience.