Well contrary to the above posts, you can do it, it isn't that hard, and is far from complicated.
Firstly I am assuming you are just popping off the barrel retaining nut, so based on that assumption, the problem is getting the barrel nut off, and then back on without the nut wrench that you can buy from Brownells etc. I just used to make my own from socket sets ground down, and a thin head ratchet. Piece of piss once you are set up, but slow and fiddly. Even if you don't go to that extreme its still do-able, I used to use quality vise grips to get it off (they need a tight, and I mean damn tight grip on some of the barrel nuts), then modify the nut with a slot on its face so I could use a drag link bit (like a screw driver blade) to just unscrew the modified nut, then screw it back on.
Made cleaning the old 74 family really easy.
As far as shift in aim, not much if you did it right, usually not more than a few inches at 100yds, which is basically what the guns accuracy usually was anyway. In truth it just seemed to move the center of the group around a bit, but not much.