What I learned in my three builds as a beginner.
The barrel has an extension ring that is attached precisely to establish the correct head spacing. This extension also has an indexing nib that aligns into the indexing slot on the upper. Most barrels come with the extension attached and adjusted, if not, you will need the proper tools and knowledge to attach it. This is where major problems arise in attempts by first time builders. Incorrect head spacing is usually catastrophic in any firearm. Make sure your barrel has the extension ring attached when you buy it.

Research,tools and patience. No shortcuts in any of these,run the build thru your head over and over before you put any part together. The research should also reveal that quality parts are central to avoiding issues such threads,tolerances etc..mixing milspec with non can certainly create problems for a beginner. Tools are definitely a must and not overly expensive.
Once you start,go slow,dry fit,check then check again. Since aluminum comes into play with many parts, I guess it would be possible to wear out a thread but if your research in parts and procedures was thorough, they shouldn't wear out in just a few attempts at assembly unless excessive force or impatience is present.

I found the bolt carrier group assembly to be more intricate and complex than the barrel and gas assembly.
Go for it, it's not hard at all once you complete one. Just think it thru,dont rusk and be certain of your parts compatibility and quality. I'm sure some with alot more experience and knowledge will be along to advise. I am happy with the reults my projects and found the last one was exceptionally easy and straight forward having done the previous two. Good Luck