Hi Jennifer Of all things I have done in and around residential construction, this is one thing I haven't done, but am intensly interested in, as we are looking at a couple of turn-of-the-century houses that have some definite wall problems.
What I have found so far is that skim coating with drywall compound is doable, but if your interest is to keep the wall look and texture original, you really need to have a genuine plaster 'putty coat', applied by a real plasterer. There is quite a nack to put this stuff on the wall correctly, and these guys (at least the ones I've seen) do it all the time and tend to be good at it. Also, if your house is settling at all, might want to consider applying a base fiberglas mesh against the old wall before replastering over it. It'll keep old cracks from opening up through the new putty coat.