Firstly if you take your bike to a shop...never expect anything to be free. If you are a regular customer and the shop is relatively quiet then maybe a freebie is a reasonable expectation. And if you can take the wheel off a bike, remove cog and lockring, grease said lockring and cog, tighten lockring and cog and then put the wheel back on the bike with proper chain tension in 2 seconds, you sir are the fastest bike mechanic in the known universe.