First off, thanks guys... it's nice to know I've learned enough here to help others.
Marty,
I'm glad to see you didn't get scared off and are taking all the right steps. I think you'll be happier in the long run with a 40G tank over your original, smaller plans.
I too agree that the Conscientious Marine Aquarist is a great starter book. Reef Secrets by Alf Nilson is another one I like as well.
As far as amount of live rock, Lando's 60 - 80 lbs is a great goal but I wanted to add that you need to be mindful of the type you buy because 80 lbs of a porous rock will barely all fit and not look too good if it does. I bought 55lbs of a porous rock for my 46G and was thinking on adding more after I judged how much more I needed after the initial 55 lbs.
By the time I finished aquascaping ledges, archways anc caves, (as you mentioned as well), I didn't feel I needed any more in there. Also, research the typical shapes and avg. pounds per piece weight in different types of rock. If you want a dramatic aquascape, you don't want to receive a shipment of 60 lbs and find two 20 lbs pieces in there, it can be limiting.
For a heads up, Many people just stack their rock until pieces "lock" together and look good. Other options are aquascaping epoxy putty and pvc framing support. I mention these because they will allow you to dream up, and carry out the various caves, archways and overhangs that you want to have. I too had the same in mind when I was waiting for my rock. Luckily, I got very cool shapes and only used a limited amount of putty. (placed after aquascaping for peace of mind)
As Lando said, there are tons of ways to go about stocking a tank this size, and tons of inverts, fish and corals waiting for you to discover and get excited about!! This site is an invaluable resource.... just keep reading and asking questions and I'm sure you're gonna find this hobby to be unlike any other.
Cheers,
Ryan