IDK if this is true (but i think i read it in a yorkie book
) but i read to make sure you actually pay EXTRA attention to the older pup...they said the younger pups are actually used to sharing attention with the littermates and will not notice if they are being "slighted" a little bit
this way the older pups know they are not being "replaced" by the little youngin and will warm up a little easier (and hopefully faster) ... good luck and congrats on the new baby!
edited: well, exactly what "yorkiekids" said
sorry, i should have read the replies better before i replied! hehe