Yeah, it works better if you're circumcised. All the uncut guys I've been with have more trouble keeping it tucked in, it just slides out in that sheath of skin. Cut guys can keep it fastened in easier for some reason. I've worn mine tucked in since 5th grade, even in locker rooms, military showers, some guys stared but nobody said anything.
I've worn my dick tucked in every day since grade school, and no, you can't pee with it tucked in unless you want to make a big mess. Just train it to stay in - it may take a long time - and pop it out to pee and slide it back in when you're done. Jacking off with it in gives an incredible orgasm.