K.
The easiest way to night wean him will be to get him out of your bed. You might check some of the message boards at www.mothering.com/discussions for tips on how to do this. I was able to get my son to sleep through the night at around 12 months, but he was in his own crib so if he woke I would just send my husband in to comfort him instead of me.
You may find that your cycles return once you cut back to 1-2x nursing per day. You can also try taking Vitex, an herb, to coax them back into existance. I started taking this when I was about 15 months postpartum (still nursing my son and hadn't gotten mine back yet) and about 7 week later I ovulated and immediately got pregnant. We're expecting #2 in June of this year, and my son weaned completely about 6 weeks ago.
I do think his habits will change somewhat when you wean, but don't worry if they don't. Toddlers are picky about eating. Just look at what he eats during a week, rather than during a single meal - and you'll feel better about him getting a balanced diet :) Continue to offer him lots of healthy choices and if you hit upon something he likes one day, let him have at it. I don't think it's worth it to make food into a power struggle - this is one of the few areas where kids feel like they can have some decision-making power.