You should also try out KTouch, part of the kdeedu module in KDE.  I'm learning Colemak right now (started a couple of days ago) coming from Dvorak, and KTouch is helping a lot.  There are KTouch lessons you can download at this site.

If you're a fast qwerty typist already it'll likely take you quite a while to match your original speed, and you probably won't see more than a small improvement. The people who get the greatest benefit out of Colemak are people who never managed to get the hang of qwerty and just hunt-and-peck on it.

I'd also strongly recommend you get a split ergonomic keyboard if you can. I personally find Colemak isn't well suited to traditional flat keyboards, but it does work well with ergonomic ones. The Microsoft Natural 4000 is my weapon of choice in this particular area.

As far as learning is concerned, don't try to go cold turkey from the word go. Just do an hour or two on Colemak in the evenings until you get fast enough at it to be able to use it at school/work without hindering your productivity. And try to remain ambikeyboardrous as far as possible -- the two layouts exercise different muscles in different ways, and I find that alternating between them is more comfortable in the long term than using either one in isolation.