Sounds like a great project!
Any time that you ship a receiver, you have to go through an FFL, that can run you an additional $25-$100 dollars in addition to shipping depending on the FFL holders fees. You might want to look into what a local gunsmith would charge to screw on the barrel and compare.
If you're a do-it-yourselfer type, you shouldn't need a gunsmith for the other stuff (assuming you get a mag assembly and trigger that are drop in fits).
Most likely you are going to want to epoxy bed the receiver to the stock and probably install action screw pillars. Both processes can be done at home as long as you take your time and do some reading on the topics, maybe practice on a junker stock too.
Best of luck and keep us updated