James,
I've done it twice so far. Whether or not it's worth it depends on what you want to accomplish. It is not very difficult if you have good reference material and a coach (at least the first time). I can't help with the books since I was lucky enough to have a couple of smiths help me with guidance.
The actual tools needed are not extensive or very expensive - several good files for medium to fine cut, especially small triangular and half round type. A Dremel tool helps but is not absolutely necessary. You'll need some very fine sandpaper (auto body type) from 320 grit all the way to 800 or 1000. I even use 1500 grit for polishing parts. Some tools are real cheap - like popsicle sticks and chop-sticks. I use the first as a sanding block for the breech face or other small areas and the oriental type works great for sanding slide stop lugs or driving pins without marking them.
Is it worth the time? Depends on you. You MUST take the time to do it right. It can get tedious and sometimes frustrating. You have to go slow and learn when it's time to put it down. Like Jim V said, you WILL learn how EVERYTHING on a 1911 works and fits together. That's why I originally built my first one.
A tip - buy as many "drop-in" or "pre-fit" parts as you can. They don't actually drop in but the fitting required will be much less. The slide and frame are the most expensive parts and many suppliers offer them in fitted sets. This ain't a bad way to go on the first one - unfortunately, I wanted Caspian for my first and they don't do slide/frame fits but they will install the plunger tube and grip screw bushings. Another tip - get a piece of glass about 1/4" thick and at least 8" square to use as a work surface when sanding flat parts. Lay the sandpaper on the glass and work to part on the paper - keeps flat stuff flat.
Also like Jim V said, you really won't save much, if any, money. If you build a true custom piece with fitted everything and premium grade parts you'll spend close to $800 or $900 on parts alone!
If you like a challenge and you want a real custom gun AND you just have to how it all works - go for it. If you just want a real nice 1911 to shoot - spend the $1100 to $1500 it takes to buy a "custom package" gun from one of the major players like Wilson, Baer, Nowlin etc.
Mikey