Ice climbers sharpen their crampons frequently, so any ice climber should be able to help you.
To sharpen, use a bastard mill (hand) file (available at most hardware stores). Do not use a power grinder--it will overheat the metal and destroy the temper.
Ice climbers may sharpen their points razor sharp, but a hiker need not keep them as sharp. Sharpness similar to the point of a ball point pen should be plenty for a hiker. You don't need them so sharp that they are at high risk of cutting or tearing your pants legs.
Just looked up a picture of the G10 on the web--it is made of bent sheet metal. Sharpen the bottom points by filing on the edges of the sheet metal. Do not thin the sheet metal. (For the point under the ball of your foot, file the thin forward and backward surfaces, not the broad left and right sides.) This will shorten the triangle-shaped point slightly.
I'm having difficulty finding a good image of the front points. If they come to points similar to the bottom points, sharpen them the same way (I think this is correct for the G10). Some crampons have a flat front point with the end shaped like a wood chisel. If this is the case, sharpen by filing the slant surface as when sharpening wood a chisel. The front points are less important than the bottom points for a hiker. (If you are on low angle ice, you should be "flat footing" rather than "front pointing".)
For all your points, you might want to debur the points with the file. (This might dull them slightly.) Burrs tend to catch in fabric tearing one's pants legs or gaiters.
Never heard of a shop sharpening crampons, but I suppose they could. If anything isn't clear about my description, you should be able to get advice from someone at a shop, or, of course, any half-way competent ice climber.
Doug