Actually, Linux isn't one particular OS - there are several flavours all the way from Debian to..
But, never mind, the fact is that it shouldn't be a problem for most tasks. It's not like he'll ask you to install a kernal and mount a disk. He'll likely expect you to use some program running in the Linux OS - and those look and act very like Windows applications. Open Office, for example, is an alternate to MS Office (and often used on Linux systems). You start the word processing (called Writer) and while it looks a bit different to Word you essentially have all the nav bars at the top and you click on File and New to start a new file - just like you would with Word. Or click on Help if you get stuck with a particular task. Most shortcuts you use in Windows, actions you perform (like double clicking) are all the same in Linux.
I use it on my netbook and it is v easy to negotiate (well the version on my net book is anyway) The only thing I will mention is that if you are writing a document on the word processing application when you save it they give you options and one of them is to save it as a word doc and I would advise you to choose that as standard as it saves a lot of to-ing and fro-ing if you are sending a doc to someone else.
Quick note: You may have already tried Open Office but if you do want to try Linux itself on your own home PC, it's pretty easy. You don't even need to install it. There are several versions (like knoppix free download) you can run from a CD or USB stick. Yes, the whole operating system runs from CD/DVD and your Windows remains exactly as it was! It's a really cool way to try Linux.