the best advise i can give is to ask them to see their own knife and if it looks like a monkey did it, i would pass.
Dang it, richard... if you are going to launch something like that at least give me a chance to set my coffee down. I laughed hard enough to nearly fall out of my chair. A monkey.... no kidding!
On the other end of the spectrum, our BP Shop has a fella in his mid 60s or so that takes a great deal of pride in working at the knife counter, his knowledge of knives and his ability to get them sharp.
They use paper wheels to sharpen at that store, and with a bit of conversation with him about knives and such he will sharpen your knife for nothing. Mind you, he won't get out any nicks, deformations, rework broken points, or anything like that. And after we compared knives in our pocket, he just buffed the edge on mine. He has a lot of pride in his ability to sharpen and it shows. Needless to say, he is probably a one in a million.
I cannot think of anyone I know or any local service I know of that I would let sharpen one of my knives. I never have. To me, owning a knife and sharpening a knife are just the different sides of the same coin. Just as owning a gun doesn't make much sense if you don't know how to use and maintain it. Sharpening a knife is a huge part of using a knife as a tool and you need to learn how to do that for yourself so you can keep it in top shape, ready to go.
There are some good tutorials on this site as well as good opinions on different sharpening equipment and how to use it. Likewise, there are good sharpening videos on YouTube. I would start at those two places.
Robert