I'm just following along with this string, and wanted to say that we were in this exact situation a few months ago, so I can totally sympathize.
We moved our LO, whom with we coslept and who nursed every 1.5 hours, to his crib when he was 5 months old. It was hard -- perhaps more so for me, because there is such an emotional side to cosleeping -- but it improved everyone's sleep so much. We were dealing with a much younger baby who needed to be fed more often at night, but we decided to tackled everything at once: we slowly transitioned him into his crib, cut down on his night feeds, and dealt with his dependency on nursing to fall asleep. The first three nights I slept with him on a mattress on the ground in his room, to get him used to his new surroundings. The next night, we put him in his crib and my DH started PU/PDs (the board for this helped a lot) and he slept in LO's room with him on the ground next to the crib. I would go in every 3 hours (or whatever wake-up was closest to the 3-hour mark) and nurse him, then we stretched it to every 4 hours, and so on, so that it wouldnt be such a shock to him. (I know what you mean about the full diapers after all-night nursing!!) It took about 3 weeks (and a REALLY bad regression), but we did it (!!!) and now he falls asleep independently (babbles himself to sleep) and doesn't wake nearly as often to nurse. Naps were challenging, but we did them too. Most days I would try for one nap in the crib and then take him out in the stroller for the second nap (they were too exhausting for me to do two a day!). Now he does both naps in his crib -- it's actually where he sleeps best!
Hope that helps in some way. Again, I sympathize with what you're going through!