Erica - I don't really know about behavioral changes since our daughter's
allergy is manifested through anaphylaxis.  But I do know how daunting
it seems to try to feed a kid with milk allergies.  It gets easier with
time - we do it without thinking now.  At first we (in the winter) cooked
a lot of roasts etc.  Spaghetti is ok, but if you buy the sauce, read the
ingredients closely - come put cheese in there.  We've found a lot of breakfast
cereals that are ok - just read, read, read.  The Food Allergy Network
is a great source of information.  I don't have their address handy, but
they do have a home page if you do a search.  They have laminated cards
with every thing milk may be called (it's a long list).  They have a cook
book (good chocolate cake recipe).  My husband and I still eat milk products,
but are very careful about not contaminating her utensils or plates.  We've
told her since she was about your son's age that milk will make her sick
and she will need a shot if she eats/drinks any.  She is VERY good about
it - just says "oh" and moves on.  If she wasn't, I'm sure we would give
up our milk products too.  Good luck.

Kass