Finally I've succeeded in enabling sideloading, via this page. Thank you, whoever posted it here, I've lost track, but this method works. After downloading Root Explorer I was offered another program, SQL Editor, I think - and that is what really ended up working, after I blew my first attempt. As long as you copy that file somewhere out of the branch of the tree it lives in you can edited it and then copy it back, overwriting the original. But don't take my word for it, I'm luck what worked for me worked for me! Follow the instructions above and you'll be sideloading all over the place.