The Pentax manual is fairly straightforward if you have a good understanding of exposure. I've seen this book recommended on here recently:
http://www.amazon.com/Understanding-Exposure-3rd-Edition-Photographs/dp/0817...nding+exposure
If you understand how exposure works, then all you need a K-5 user guide for is to find out all the ways you can set the shutter, aperture, ISO, and EV adjustment - these precepts are the same across all camera manufacturers.
When I came back to Pentax, I found that I needed to really understand exposure much more than I had with Canon. I've found that my Pentax is a much better tool for making pictures than my Canon was, but I need to know more about what's going on in the scene and what exposure I want.