Carrion did a great job of answering your questions, I'll just add in a bit more stuff.
First, how long does it take for callouses to form and how long do they last?Carrion explained this well; I just want to add that you should stop playing when your fingers-tips start to hurt. You'll get some really messed up callouses otherwise, as I learned the hard way. They were actually so flaky that they began to catch on the strings while I was playing. Also, on some guitars the action is ridiculously high, making it very difficult and painful to press down the strings, so you might want to have it lowered by someone who knows how.
Do I really need to use a pick? Finger picking is a lot easier, more accurate, and sounds just as good if not better, since I can more easily control my volume. Will I be able to learn to do this if I use a pick?As Carrion said, it depends on what you're looking for. I myself think it's better to use both, so that you don't limit yourself in any way. One of my old guitar teachers only used his fingers; I use a plectrum and fingers in equal amounts. It's personal preference, really, although if you want to try out fingerstyle guitar, of course you'll have to use your fingers.
I've been teaching myself for the last couple of weeks, from books and the internet. Will I ever need to find a real teacher?I think a
good teacher can really benefit you. But as with every profession, not all teachers are great at what they do. You'll come across some people who have about as much a clue as you do, and who'll just give you printed tabs from simple chord songs every lesson and tell you to learn them. (Personal experience. I finally realized that she was a rubbish teacher when she was trying to show me how a particularly challenging chord should sound, but couldn't because her fingernails were too long). But my next teacher was great, and really helped me to improve quickly.
TL/DR; I think teachers are worthwhile, but only if you can find a good one. ALSO, continue to learn things by yourself at home even if you do find a teacher. You'll progress twice as quickly.
And, perhaps most importantly... how soon will the ladies start throwing themselves at me? 
Two months tops

Although, a request; please, please don't become a cocky show-off. People will always respect a bit of modesty. Don't be afraid to showcase your skills, but at the same time don't ever get a big head, and don't look down at/try to one-up your fellow guitarists.
Mumblemumble. It isn't a competition, after all; we're all just music-lovin', instrument playin' people doing what we enjoy.
Did I mention that I
hate cocky show-offs?
Oh, and practice every day. Preferably with a routine.
Here's a good website, although there're probably more out there:
http://www.justinguitar.com/Best of luck, hope I helped slightly.