Ergonomic or not, if you're getting a new keyboard, get it sooner rather than later, and practice with it. Using a netbook most of the time, when I use another keyboard it throws me off.
As for the desk, I wish I had one
If your back starts to hurt, change your posture until it's more comfortable, like tilting your pelvis(forward and back, not side to side
) and straightening your back. Try to get the monitor at eye level so you don't have to look down at it, too. (I have my desktop's monitor sitting on a box on my desk for this, and my netbook is sitting on a textbook)