i am on ubuntu, and want to download the litecoin wallet. i'm not an expert though and dont really understand how to unpack these tar files etc.
is there a simple command i can use like "sudo apt-get litecoin_qt" which will set the wallet up for me?
Not in the actual ubuntu repositories. You'd have to look for a third party repository which might be maintained by someone who isn't necessarily friendly to your interests.
The safest option is just downloading the official tarball and building it yourself. It is safer by leaps and bounds.