How can I list all the assemblies that are in the GAC? Do I need a tool that makes it easy to view them?
You can use gacutil provided with Visual Studio for that. Simply open the Developer Command Prompt (available in Start Menu>App>Visual Studio) and run the following command:
gacutil -l >yourassemblies.txt
Gacutil is also available as a separate download if you don't have/want Visual Studio.