Well I am a noob.
Here is what I used to get started:::
Editing Manila Tutorial, has walk thru for everything you need... includes pulling files off the phone, editing them, and putting the new files back. Very nice.
http://forum.ppcgeeks.com/showpost.php?p=1204218
And I believe everyone agrees that HD Walls is the way to go for wallpapers/backgrounds. The "BG for all pages" just jacks things up. You can find it here.
http://forum.xda-developers.com/showthread.php?t=503511
Hope that helps.