The MAIN thing is the sooner the better! My pediatrician (that has a local radio show) recommends working to get them to sleep through the night at 6 months, since they are too young before that, so you are at a good age if you go for it now. It only gets harder the longer you wait. Not sure if he's napping in the crib, but if not...start with naps in the crib.
I had my 6 month old out of town on vacation and he slept in the bed most of the time b/c he was so sick. I'm a huge advocate of not having babies in the bed with you, but had to under the circumstances. Was frightened to get home and try to work on getting him to sleep through the night and back in his crib. He was the same with the crying and thought it would be so hard, but gave it a try and he only cried a lot the first night and subsided more and more each night and was sleeping through the night by the 4th day. I didn't expect it, so I'd say, just try and see just in case it's not as hard as you'd thought. Just be sure he has a night time routine that is exactly the same each night so he knows what to expect. Ours is bath, books, I hold him and sing to a nice cd with the lights down and put him in the crib and say prayers and sing. Knowing what to expect is big. I'd start with that for a week before moving him if you don't have a routine already. Sorry...didn't mean for this to get this long!