I don't think you're going to have much luck in finding someone who knows how to fix it. These Shimano hubs are fiendishly complicated, and there were a number of poorly documented changes to the inner workings thereof. But then, you know that if you've read Sheldon Brown's page on them. I would say that your best bet is to take the thing apart and put it back together again, see if that works. If it doesn't... honestly, who cares if the hub is perfectly preserved? It's still a junky hub (why did you take it apart if it was in good shape?). You'd seriously be better off with finding a Sturmey-Archer AW or other 3-speed hub to replace it. Other than that, I think the best advice that you'll get is "try, try again."