Hmm... Well for Hackerslab you can pretty much play around. To be honest that site is pretty good at helping people do there challenges. I say you should ask on that site, you will get alot better answer for there challenges.
But I did the first couple ones, a while ago. To do the first level, you should just worry about begginer stuff. Like whoami, ls -a, and pwd, cd. Those are pretty much the only commands that you will need for that one.
I don't know if you know this or not but when you telnet to the hackerslab server you are connecting to a Unix system where you have an account, and while there you under a Unix system.
As for languages you are going to have to choose one that you like. If you choose a language that you don't like you won't want to learn it and will get no where. Ex. I hate VB, I just don't like it. So I won't use it at all.
No offense Hellforge but happyhacker is a shitty site alot of there info is wrong and alot of that **** she just makes up. I have read over some of her tutorials and felt like I was dumber after I finished reading them.
For a variety of general information, that is both informative and entertaining you should ceck out Ed Skoudis' page.
He periodically issues hacker challenges done in a parody format (Matrix, rudolph, Lord of the Rings Etc..) and ties it to a vulnerability, or class of vulnerabilities. They are all still available on his site, as well as the wining answers he recieved for the challenges. You could read the challenge, do your best then go back and check the answers on the site. Just a suggestion.
By the way Ed is the primary instructor for SANS Track IV, Hacker techniques and methodology.
And I agree Happyhacker is next to useless.
From what i remeber, hackerslab.org was one of the better sites for rolling up your sleeves and getting down and dirty.
I think i made it to lvl 5, after that i think it started getting into shell scripting and that was beyond me at that point.
Pretty cool site, with some pretty need solutions. First one is pretty easy but yet gets the juices flowing..
One thins is for sure, if your week in Unix, like I am, nothing is better then being challange...getting out your favorite Unix/Linus referance guides and getting down and dirty with some now unix commands to add to your vocaubulary :-)
The best advise I have is READ...READ....and when you finished with that READ some more....and also stick around here, lots of good info if you read the posts.
Hope that helps!!