Loops 101

Suppose I want to use loops to compose a 12 bar blues in the key of C major. I find a suitable guitar line that vamps on a C major chord. At bar 5 and 6 I want the guitar to play a F major chord. Do I shift the pitch for bars 5 and 6? What if I want to use a more complex chord such as an augmented chord/ Can I do that with a loop?
I am obviously a newbie. Can anyone recommend a tutorial/book that goes into more detail than the "Copy loop A to measure one, drag it for 8 measures and you now have a song" approach.

As kicker said, groove clips won't change the chord structure, they'll only shift the whole chord equally. This works well for small timing/key changes, but is not very natural sounding past say, 4 or 5 semitones.

This kind of groove-clip looping is great for rough arrangements and allowing drag-and-drop flexibility, but it doesn't sound realistic if you're using drastic changes.

There are tons of loop CDs available that have all kinds of key- and time-coded riffs (already "acidized" or "groove-clip-ified") that you can drop right into Sonar (Funk riffs in all keys and lots of time signatures at many tempos, for instance). There are also freely-available loop librabies that do the same. Your best bet is to find stuff that already very close to what you want, and use groove-clip features to tweak stuff that's already close.

Cheers.