I used Jay Gordon's method (modified for us) with both kids. Ds was 20 mths when I did it and dd was 18 mths. I personally don't think it's a good idea to try to nightwean AND end cosleeping at the same time. I think it's too big of an adjustment for a baby or toddler.
A couple things that helped us succeed:
1. I nursed and offered food all day during the day to make sure my kids were good and full and not trying to make up calories at night.
2. I had a sippy cup of water by the bed to offer when my kids woke up. Ds always took it, dd never would. Go figure.
3. I wore non-access clothes to bed, lol.
4. I really worked on the whole, "We nurse when the sun comes up, but we sleep when it's dark." Can't remember what my little mantra was, but it was short and sweet and repeated regularly during the night and day. When 6am came around and my kids would wake up, I would make a big deal about how, "Look! The sun's out. We can nurse now! Yay!"
5. Ds was the hardest to nightwean. He was very upset, but I held him and loved him and consoled him. I walked him around if needed. I offered a drink of water when he woke. It took him 5-6 days to realize that I really wasn't offering the breast any more at night. He still woke a few times a night for several more weeks, but it was always just for a cuddle or a drink. Dd, otoh, was a breeze. She would fuss for a second, then turn over realizing it just wasn't worth it to fight for her "nur-nur."
I have to say that I thought about nightweaning ds for a few months before I actually did it. You have to prepare to not get any sleep for the few nights it takes. But, I was 6 mths pg with dd when I nightweaned ds, and I was 3 mths pg with this baby when I nightweaned dd. My own exhaustion and excruciatingly sore pg breasts were the motivation I needed.
And I have to say, with ds in particular, he really *was* suffering from lack of sleep by nursing all night. I know that cosleeping is wonderful and important, but I think in some children, the waking can become habitual and unhealthy if it's truly interfering with their sleep. After my ds nightweaned, he became a different kid--happy, content, energetic. His 45 minute daily catnip became a solid 2-2 1/2 hour nap with no effort. He slept from 7-7 without a hitch. He really needed more sleep. Dd still wakes a few times a night, but her naps have also increased in length. I still think she could use a little more sleep, though, so I'm looking into black out shades for our room.
I hope you find a good solution. Here's Dr. Gordon's article if you're interested: http://www.drjaygordon.com/ap/sleep.htm
ETA: We transitioned ds to his own bed about 3-4 months after he nightweaned. It was really easy, I think, because he was only making one change. He sometimes came into our room, but we put a blanket and pillow down for him which worked well.
We have transitioned dd to her bed, too, but she comes in to our room every night. We just got a king-sized bed, though, so it doesn't bother us
Pretty soon, I'm going to have to encourage her to lie on a pillow and blanket so I have room to sleep with the new baby. But for now, I'm just going with the flow.