Yep - the Gimp is good - but I'm not so sure about it for a novice - it's up there with Photoshop, verging on the professional and is renowned for non-intuitive user interface.
Can I suggest using PhotoFiltre until you get the hang of things. It's much simpler to use, does most things except for red-eye correction (loads of other simple programs out there for that) and layers (but I consider them to be more for the expert).
Oh ... and did I mention it was free. Find it under the freeware at
www.snapfiles.com along with many other simple photo programs (yes, and the Gimp is there too if you still fancy a look at it).
Les