Last year the AC was nice and cold, this year it does not seem as cold, does this mean I have a leak in the system?
Yes it could but there could possibly be other problems. You should have it checked out at a shop if you are concerned about it.
You may. I would bring it to a local INDEPENDENT A/C shop. They are often combined with radiator works up north. Have them check it.
If you are asking the question is not likely you have the tools and skill to do a proper measurement, let the guys with the right tools and materials do this one.