Re: To build or not to build???
When folks are talking about building it yourself, many are talking about using an assembled upper. If this is your first one I'd highly recommend against barreling it yourself. You need the vice blocks, the wrench, and you may need the torque wrench since this will be your first one.
I'd get the TM armorer's manual for building it. The one for the M16 whatever will work. Make sure you get the armorer's manual though.
For assembling a lower, the correct roll pin starter punches and a good set of punches will make it look better. I've seen taped up vice grips before --that is not how you install a roll pin at home. Those punches set me back about $20-$30 I think.
Midway sells a toolbox that has all the AR gear in it for a little over $200. If you plan on building a few, do this. Look on local forums too, some folks do "build parties" where they get together and share tools and know how (and parts too).
When assembling an upper, you can usually get away without headspacing it. IF the parts were made well, pass QC, in spec. and all that. For instance, I've seen an AR barrel not properly reamed --good old Oly. That could have been bad.
I build mine because I can't get what I want otherwise. Is there a specific setup you want that you can't get? Or do you just want to spend more on this rifle so you can put it together yourself? Are you better than the factory? You should ask yourself these questions, seriously. I'm a bit of an AR fan I guess, not that it is anything all that special but I'm REAL familiar with it so I use what works for me. If Noveske or LMT (I use both of them for parts) made exactly what I wanted and it didn't cost $4000, I'd get it. Where I save most is when I build cut rifle barreled rifles using top of the line parts assembled into a rifle not on the market.
Finally, if you want it built to order and don't have the gear, some places will do it for you. Rainier Arms will build you a rifle and they have good parts, I use them a lot as they are local for me. Even though I have the gear, I'll get the parts assembled if I can and if it costs the same or less.