Usually keeping it out of direct light for two weeks to a month is what most of the books/courses say. What I have seen, is that as soon as the tree starts growing new shoots, it can slowly put back in the sun. I have seen/read many different ideas about fertilizing after a repot... I have found that waiting for a period of weeks is a good idea, but sometimes it depends on the species.
As far as Chinese elms as "indoor" trees, I would have to disagree. I have one that I aquired last year that was trained indoors. I put it outside in the early summer, and it has stayed outside through winter. It didn't lose all of it's leaves, and I did give it some protection from the freezes and frosts in the winter, just to be a little more sure that it would survive, and it has literally exploded with new growth this spring. I might post a thread with it's development, if I can find some older pictures.