Definitely learn to create and edit your child theme's functions.php.
Justin (Hybrid) and Ian (Themeshaper) have a few great posts on the subject.

In fact Ian just posted a piece at Themeshaper which is a real eye opener for me as far as writing functions and using action hooks.
It's here

One beauty of both of these frameworks is that they provide you with a lot to hook into.
Once you start to get the basics - it's actually pretty fun to do.

UGh - sorry -I'm obviously having problems posting a link!