oh dear i think it'll be like starting from scratch and you may end up bringing him back up to the bedroom because he will probably be like the first time, crying/howling constantly for hours and nights but it depends on how much you want him out of your room because you'll have to be veryyyyyy strong and resist going down/bringing him up/you sleeping downstairs etc.
Sorry but i haven't had the experience of him being in our bedroom. When we brought Monty home at 8 weeks he howled, howled, yelped, barked the house down for a few nights and we were very upset about it all and concerned about neighbours etc but i knew that if we didnt stick at it we would be creating a rod for our own back. He settled after 2-3 nights of this and is wonderful now at nearly 5 months, not a peep out of him. (if we didnt have young kids we may have given in to his cries but i knew I had the kids etc to think about)
All I can say is be strong, maybe have a few drinks to knock out the sounds
and possibly do what i did... put my ipod on so i couldnt hear him because I was getting more upset than he was i think.
Good luck and stick at what ever you decide to do, don't give in because that will be it.