Yes, all of your Ranked stats will be wiped, but, according to this, it will still affect where you start out from in the new season and your skill level.
Personally, I wouldn't recommend trying to play champs from every lane. I'd get good with several champs from 1-2 lanes; I specialize in ADCs, mid lane APCs, and supports. You don't want to be play a role you're not good at, even if people tell you that you should. Queue dodging will prevent you from playing, starting from 5 minutes 30 seconds, then 30 minutes, then 1 hour after every additional dodge. Again, only play champs that you feel comfortable with playing. People will be more irritated if you play a champ that you're subpar with than if you queue dodge.
FYI, the number of wins doesn't matter. How good you are with the champs you're playing does. Experience > Number of wins every time.
Also, you should know that if you're placed in Bronze, there's a high possibility that you'll be there for a while; Bronze is filled with the people that play ranked games, but aren't good enough to rise in ranks. They're famous for being unhelpful, spiteful, flamers that hate you for doing better or worse than they do. I've heard horror stories about Bronze, and the trolls, flamers, and feeders can keep you in "Elo Hell" for a very long time.