I've been in and out! The 'Digital Photography' is a lot of tips, but some of them are really useful! I have yet to really get into 'Understanding Exposure'. So much is trial and error! Have fun!
You can change some settings on P, like the ISO, White Balance, Metering, etc. But, not necessarily the aperature and shutter. You have to use those priority modes to change those settings. Or Manual. It totally helps to look at the camera! And, frankly, I gave up reading the manual because I am so much better with hands on. I took a class specifically for the D40/D60 and it was soooooo helpful. It gave me the basics so that when I read books, I know the background of what they are talking about.
Re: *j*w* I replied below.