three feet tall seems pretty small already for these shrubs. I'd do some hand pruning to make them more attractive but anything more severe will leave unattractive stubs.

No harm to prune them now.

Sounds like they are too close together. Your new buyer may want to do some transplanting.

I don't see why not: to my knowledge, they don't "bloom" like an azalea which I've always been told to not prune the azalea until the blossoms are spent, so, I've chopped my azaleas way back last year, and they came back this year, but the early "warm" weather screwed things up a little. They bloomed before the first real warm spell came about, and the quick freeze knocked back the plants just a bit. anyway, not to get off track, I don't know of any reason of not to trim the bushes back.