I would think anyone willing to do the job would be able to send pictures of their work, so you could determine whether it is the quality/style/etc that you're looking for.
Learning to do it yourself is a good option, if you're going to do more than one, or a few. Otherwise why waste the time learning something you're not going to use again?
Another thing to consider are the surfaces. Whether you, or the hired help are going to prep the surfaces for the carving and engraving? Smooth surfaces for the guy to just have at would be the best bet.
Why don't you post up a few pictures of the engraving detail you'd like. Same with the tang shell. Also, the area your at. You could ship the parts to engrave easily enough, but shipping the gun for carving is another matter.