We co-slept from birth, as well as breastfed, DD is two and is in her own cot in her own room now, and is totally weaned (want to change to a bed but haven't had the guts to do it, but thats a whole other story lol)
We just slowly progressed with it all when we wanted to change. Initially we side-carred the cot to our bed and got her to sleep in that so she was still near us. Then when she was well and truly used to that, we put the side up on the cot, but it was still side carred. Again, once she was very used to that, we moved the cot to the other side of the room, then finally, into her room.
Meanwhile, during all this, we were teaching her to self settle (no CIO or anything at all here though) mind you there were a few tears, but they were protest tears that she wasnt tired or didnt want to sleep, lol. It never lasted long and she now LOVES her cot and loves her sleep. We've never had any issues with sleep at all, because we did it all at HER pace.
This whole process took maybe 6 months to get her into her own room and sleeping through the night.