1. My menstrual cramps are (er... were, as they still haven't come back yet) bad enough that they often woke and kept me up at night. I would double over from the pain and audibly gasp from them. That didn't even compare to actual labour. I didn't scream or go crazy, but I did cry and want to give up, so I think that's mostly a matter of personal temperment. You do keep your temperment in labour, it's just that the worst parts of it come out. I'm not inclined to screaming or getting angry, so I didn't. Early cramps were impossible to sleep through, though I catnapped between them. Those were not quite as bad as my menstrual cramps. Once my dilation really started progressing I ended up writhing off of and gripping the bed fairly consistently. The movements were close to those I make during a really great, overwhelming orgasm, actually. Got an epidural, but all it really seemed to do was slow my labour/slow my baby's heartbeat, and it had completely worn off by the time pushing came. Wasn't too bad at that point except for feeling like my hips were going to break apart. Dislocate a joint. Keep pulling for hours at a time. And then try to exert yourself and actually accomplish something through the pain. That was the worst of it, for me. That pain killed everything else once he really started coming out, though I could certainly feel the contractions just like in the beginning. I really can't think of anything that compares to the pain level. Not that I've experienced. It was, probably, up to 15x the intensity of my normal cramps... but it's a poor comparison.
2. I tore. They also gave me an episiotomy. I had star-shaped tearing all around my vulva, in fact. They stitch you up, and it is quite common. Took me three months to heal the wounds completely, internally and externally. Part of this is my fault for not settling down and letting myself heal though. I wasn't in pain, in spite of being pretty badly wounded (good pain tolerance), so I just kept moving.
3. Mine looks the same outside as it did before, at least as far as I can tell. It feels the same, at least. Internally it feels different. There seem to be more twists and turns, it's a little tighter, and my cervix feels a little scarred now.