Any place I can get instructions to do the above. I know there is more to it but seems to me you torque down the barrel, throw a bolt in it and shoot. This headspacing thing is also a mystery to me. Any info would be appreciated.

Almost any new barrel you buy (from a reputable company, such as Colt, BM, DPMS, RRA, etc.)will already be headspaced, so you shouldn't have to worry about that. In fact, you'll have a much more difficult time finding a new barrel that ISN'T headspaced.

If you are assebling an upper, and have a barrel/bolt combination that didn't come from the same source, you shold check it.

Here's how I do it.

First, I take an empty cartridge that has been fired. The bolt should close on this.

Then I take the bolt apart, remove the ejector, and the extractor.  Put bolt back in carrier, and try to close on the headspace gauge. (Availalble at Brownells I'll get you the part #)

Try to close the bolt by pushing on the rear with your fingers, it should not close.

The trickiest part of the whole procedure is removing the ejector.  Wear eye protection, and/or do it in a baggie.

Actually, it's pretty much that easy - just tighten the barrel nut until the next gas tube notch lines up and that's it.  Here's a few threads to read - it'll save us from retyping all our usual flames over again. [:D]

[url=http://www.ar15.com/forums/topic.html?b=3&f=4&t=162176]This one[/url] and [url=http://www.ar15.com/forums/topic.html?b=3&f=4&t=161133]this one[/url].  Good luck!

Regular headspace gauges won't work on Colt barrels.  A standard field gauge will close on a Colt barrel and misleading that it's excessive.  Colt has it's own gauges.