If you can find them, the old DMR books for 2nd edition have some great advice. I recommend the first two, then five. In addition, the World Builder's Guide and the Dungeon Building Guide, both very good.
In 3rd ed or neutral, you have Robin Law's Master's of Game Mastery. Then we have the book by the people who did Fudge, GM Secrets or something. It was okay. Good for a new GM. Then we have Johnn For. Look for his website, buy his book on NPC creation/use, buy his disk with all the articles indexed. Great resource there.
In terms of starting modules, yes, Orcfest is a great adventure. Goodman Games has many 'classic' or old style dungeons if you will that don't require a lot of work to integrate into the game and are easy to run, if you want to run a dungeon.