The Help menu in HackBuilder contains information about each of the hacks in more detail than the names provide.
Here's a link to very good instructions on flashing:
https://www.mobileread.com/forums/showthread.php?t=12573
Also, don't worry too much about bricking your reader. It's a little scary the first time, but it's pretty easy to recover from. I've been doing a bunch of development, bricking it back and forth, and have recovered every time.