Build difficulty ?

[dmsims21]

I don't think it is that difficult, as long as you get the right parts. Putting one together isn't too bad, but building one that functions properly is a little more difficult.
Many times when you read of horror stories on the internet, it is due to components not working well together. Not everything is completely standard.
The gas port may be the right size and the gas block lined up, but the buffer of the wrong weight.