it's so easy... I would say much easy than installing windows
first, you don't even need to install it to try it. Just download the bootable cd and you can run linux already without installing it (ubuntu).
Once I was done playing, for a bit
I de-fragmented my hd using windows

that took the longest. then I restarted the pc using the ubuntu bootable cd.
and followed the 6 steps to install it.
In one of those steps I was able to reconfigured my partitions (I made two new partitions)
other steps were like: name, pass, and timezone
and that was it.
you can install linux while surfing online
I didn't have anything important on my hd... but what I had it's still there. Windows work.
I didn't had to type any cd-keys to install anything and it comes with "MS-office style" tools

like word processor etc.