There are big problems with building an ak47 type firearm.
the barrel press issue. You have to have a means of pressing the barrel into the trunion so it is square. A press and jig for doing this is pricier than the gun off the shelf.
The barrels that come with these kits have already been mated with a trunion and drilled for pinning then the trunion removed. Since its already been indexed once you now have the big issues of either re-welding to get a proper index or hoping the new trunion indexes properly or fixing any cant issues if they arise at the front sight base instead. Its potluck for this.
It can be done and has been done but usually by folks that have access to an extensive machine shop or the tools needed. Its not as simply as building an ar15. The ak47 was designed to not be repairable for the most part hence the riveting and welding together of parts. Its a toss away firearm. Something major goes wrong toss it get a new one.
"Gun control: The theory that a woman found dead in an alley, raped and strangled with her panty hose, is somehow morally superior to a woman explaining to police how her attacker got that fatal bullet wound." L. Neil Smith
The problem with being stupid is you cannot simply decide to stop doing dumb things...