Rob,
I am by no means an expert, but I did spend some time looking reasonably thoroughy into the feasability of doing some engraving, The real McCoy consists of "carving" grooves in the surface of a metal plate using specialized hand tools something like miniature wood carving chisels.
There are power tools available now, not cheap, and videos that show how to use them.
I think to ask the question "how hard is it " is reasonable, but the answer is not simple - how hard is it to cut a dovetail or pinstripe a fender ? Recall that engravers are skilled artists who used to serve an apprenticeship like many trades, and so "how hard it is" depends on exactly how complex an engraving job, and how demanding you wish to be about the result.
Having said that, I am fairly sure a skilled and handy-with-tools person who wants to take the time and trouble and expense to learn the trade can probably do a credible job - but not in a few days. Think how long it took you to produce professional looking dovetails, cut entirely by hand, as an example.
Karl