Don't think I'm a horrible, mean person for saying this, but you've got to stop giving in. You know you need to stop using it as a crutch, so stop using it as a crutch. Your little boy won't like it, but he'll figure it out in no time at all. Our babies are a lot smarter than we think.
Lay him down to sleep while he's still awake. Again, he won't like it, but no child ever cried themselves to death. Go in there a couple times and soothe him but LEAVE HIM IN THE CRIB. Stop waking up to nurse him. He does it because he knows he'll get the soothing and because he doesn't know how to get himself back to sleep without it, NOT because he's starving to death. He won't like that either, but he'll figure out that when he cries, nothing is coming, and he'll eventually learn to stop waking up for it. And by 'eventually,' I mean a few days, not long.
I think everyone does it differently depending on the child, but when I weaned my daughter I went to nursing her in the morning when she woke up and at night before putting her to bed (awake! ;). I then cut it down to only at night, and then just stopped doing it altogether (and she didn't even seem to notice - but all babies are different). I don't remember the interval of time between each - maybe a week or so. Really it's more how you feel about it.
We mothers love to make our babies happy and we hate it when we have to contribute to their displeasure. Unfortunately, discipling them takes discipling ourselves to do what is the best for them (even though they may not like it!). It's hard listening to your little one cry when you know you have the cure, but he needs to learn to sleep. You know this, and so you've got to step up to the plate to do what you know will be the best in the long run.