NOt a motorhead, but want to try

Intake and Exaust,
More air IN, and more air OUT, is always the best to start.

Chiltons, Haynes, and most of the Hot rod/5.0 mags put out small block how to books and videos in some cases.

The regular car manuals will have all the torque specs you should need while working.
Its not real hard, with a little luck.
The only thing i didnt trust doing was torqeing, shimming, and setting the main berings.
Had a friend do it that had more experience.
Rebuilding an engine the RIGHT way, take a lot of time and MOney. There is A LOT of stuff to do it right.
Basicly read everything you can get you hands on, check out the 5.0 mag sites for their tech articals, google a bit, and keep reading till you feel comfortable and have enough saved to do it right.
Thats the best i can give for advice.

(one more thing, look into a Short block, that is already done right, it can save alot of time and money, not to mention some hidden bugs you may not even know about till after its apart, that will cost more down the line)

Keep an eye out for a Explorer motor, that's the best budget performance thing going now. At minimum you'll have to change the cam, and valve springs; then use your Mustang accessories and ect to finish it off. There are a ton of write-ups on how to do it, I searched for the write-ups and built the motor long before I joined a forum. Do your research, ask around, and you should be able to build a good motor the first time around.

Its not that bad of a job . PAY ATTENTION TO DETAIL. Always replace oil pump.
I built my motor years ago and just got done building a 4 cyl 2.3 for my brother-in-law yesterday. Chilton or Haynes manuals are fine they have all bearing tolerances and torque specs, make sure you look at the correct engine, those manuals have all engines specs for 4,6,and 8 cyls.

if you can get someone with expierience there to guide you. All the haynes chilton and mags could help out too. It will take time and lots of elbow grease but that is the best way to learn.