shop repair question

I have a 2011 chevy camero and I had some coolant prolems with the oring in the back of the engine, so I had a shop fix it. While I had the car there I also ask them to due new spark plugs and an oil change. When I got my car back it started skipping and the engine light came on, so I took it back. I was told that the number six coil was not good. The owner showed me the coil and the rubber around the coil was all mested up. Now the car had no prior problem with this until they worked on it. I had them chage them because it was time at 100,000 miles for maintance. I see on the internet that you have to take out the coils in order to change the spark plugs in this car. My question is could the coolant problem have any thing to due with this happening or could this be from them putting them in wrong? I think they would have notice the coil was like this if they had to take them out, before he put it back in.