Some of the best advice I can give you concerning sharpening lawn mower blades is to always have a spare set on hand. This way you will be able to continue with your lawn cutting if your blades become unusable.
If you are not very experienced in removing and installing lawn mower blades and know which side is up and which side is down, mark the blade before you take it off. Use a tool to scratch the blade or a can of spray paint. Mark the lawn side so you will know that side faces the grass when reinstalled.
You can sharpen your blades yourself. I certainly appreciate the business but if you would like to, you can do a very good job yourself. Just remember that a lawn mower blade is not a knife. It does not need a sharp knife edge. In fact, if you sharpen the blade like a knife, normal lawn cutting will quickly destroy the edge. Sand, small pebbles and miscellaneous bits of hard debris hit the cutting edge of lawn mower blades at a very high speed. A sharp blade cannot hold up to this type of assault.
When you sharpen your blades, sharpen them only as sharp as a butter knife edge. That edge will last ten times or more as long as a knife sharp edge.