C.,
I don't think 3 months is too young at all. My children had established sleep patterns by then, and actualy were sleeping through the night by 8 weeks. Babies establish these habits and patterns by us, the parents, teaching them how and when to sleep. Parent having more wisdom than child. Order vs. chaos. We actually let them cry if necessary from the day the came home from the hospital. If they are fed, burped, dry and ready for bed, and there is no other reason for them to be crying, they need to cry it out. If you keep going to them, you become their sleep crutch. Yes it's hard. Times my hubby had to hold me back from going in the room, times I had to hold him back. But it only happened 2 times. A child learns quick. Obviously, this was at nap and bedtimes, and you learn your baby's cries. You know when it is a "I want my way" cry and when it is a distress cry. The baby get's plenty of time being held, so don't feel like you are depriving your baby of being held and nurtured. That's a bunch of nonsense. Part of nurturing is training them.
That being said, I would definately try the swaddle routine. My daughter LOVED being swaddled, and so we did it. For 9 months. We had to find a bigger blanket! But it was how she felt best for sleeping. Each child is different, but the child MUST learn to settle themselves and 3 months is not too early to begin this. Otherwise, you may end up with the scenario I had with my firstborn. Even at a year or later...rock him to sleep with a bottle...pull the bottle out and rock back to sleep...stand up...sway back to sleep...put in crib, pat back to sleep...duck out of sight...crawl out of the room...RIDICULOUS!!!! The other 2 we put them down awake, helped them learn to fall asleep on their own and now we have GREAT sleepers and nappers. Sometimes my 5 y/o even ASKS for a nap! Often my 3 y/o will wake up from a nap (early) and I just leave him alone and he goes back to sleep.
Hope this helps!