AK build discussion barrel populating

I'm interested in getting into AK building.and have found most information i need. The part I'm still having trouble wrapping my head around is populating the barrel. And I have a few questions.

1. Should the barrel be pressed into the front trunnion before or after the front trunnion is riveted to the receiver
2. What is the best way to ensure the gas port will be aligned properly when pressing in the barrel
3. Is any additional drilling into the barrel required for the gas block and front sight post

Barrel needs to be populated first. Unfortunately I don't have answers to your other two questions, hope this helps a little.