Hi Blackcat, I ve started leatherworking some months ago and I remember having the same questions, and I can assure you,here you can find the answers you'are looking for... I've learned a lot from this forum and also watching a lot of tutorials on youtube.
I make too western rigs and for what I I know metal lined holsters are for Cowboy Action Shooting (CAS), I don't know very much about metal lining and I'm willing to learn more, I'm sure someone will give you some suggestions.
The leather recommended for gun leather is generally 8/9 oz leather, since I'm from Italy we have a different mesurament system, we use millimiters for leather so 8/9 oz is generally 3mm.
Of course you can stitch by hand, the most common used method is saddlestitching, and there's plenty of tutorials here and demo on youtube.
If you want to learn how to make great and functional western holsters, you have to read this guide by Jim Simmons is simply awesome and explains pretty much everything!
http://leatherworker.net/forum/index.php?showtopic=19338
Here you can find also some great patterns for getting started on western holsters http://leatherworker.net/forum/index.php?showtopic=19714
I'll also send you a link you to a great video on making cartridges loops for belts
Richard Black always explains the tools he uses and that you will need, I suggest you to watch all his videos, helped me big time with his tutorials.Hope it helped
Cheers from Italy
Bruno