There's not really any simple guide to AltEPG. The closest we've got are the Announcements topics under the "Installation & Configuration" section of this forum (
viewforum.php?f=16). These will tell you about AltEPG specific stuff. If you're seeking information about general TiVo hacking (telnet, bash etc) then I'd recommend the O'Reilly book "TiVo Hacks". Published in 2003 and out of print no doubt, but it still gives an excellent grounding all things TiVo. You can get an electronic copy here:
http://shop.oreilly.com/product/9780596005535.do, or you can pick up a used hard copy from amazon or ebay for a snip.
Regarding the hacks supplied with the AltEPG image, there isn't a published list as far as I know, so I will take this prompt to produce one. Watch this space.
There is a hack for sorting the now playing list ("sortnp"). This isn't included in the AltEPG image but if you've got a network card you can download it and install it. Put sortnp into google and you'll get some sites where you can download/install it from. Have a go at that and see how you get on.