Alright good news.

It appears all you need to do is copy the SimpleCalculator dll from your project folder to the bin directory in you site directory. I don't even think you need an additional line in the web.config which is confusing to me bc I thought IIS would execute any code it didn't deem as safe in the web.config. I don't even know if signing is necessary.

As far as the GAC is concerned, my guess is that the server reference at the top of the ascx file would need to point to somewhere else that tells it the DLL is in the GAC, it doesn't appear to automatically look there by default. Hope that helps.