** Is it fairly easy to add on a dryer outlet where a 220 range outlet currently exists? **
I don't know about "adding on" but "changing" the actual outlet from one for a range to one for a dryer should not be difficult.
However, since each of those types of outlets should be fused differently in the house fuse panel (dryer=30 amp, range=40-50 amp), the fuses/breakers for the outlet should be changed as well. It is not a good idea to have an over-fused outlet as that would basically negate the purpose of the fuse to begin with.