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.