If you're living in Oregon they just passed ballot measure 114, which means that you can't have magazines with more than 10rds after a specific date, and also that the cops (Like the notoriously fascist Portland Police Bureau) get to decide who can and cannot own a gun.
But there's a loophole; Get your magazines before 114 goes in to effect and you can keep them, although you are required to prove that you bought them before the day of doom.
So if you might every want to get an AR, or just feel like it, it might be worth it to pick up a bunch of mags now and box them up with the receipt just in case.
A complete upper and a complete lower click together with two pins. The only pieces you need special tools for are the castle nut that holds the stock in place and the barrel. Installing your own bareel is kind of a pita bc you need an armorer's wrench and a torgue wrench and it's just a pain to do by yourself without specialized clamps and shit. But the lower is easy. As long as you have some roll pin punches and a decent basic tool kit you can do it if you're handy. Make sure to get some extra detente springs tho because if those fuckers go flying you'll never find them again.