To get the sun roof shae out, you need to pull the headliner out. I was able to glue down the front areas on my shade that were coming apart, with some rubber cement.
The problem with one side being colder/warmer than the other is probably your mix actuator. Here'* one thread on the subject http://www.gmforum.com/t280678/
Use the forums search feature and look for more info on heater and ac.
also, please add your year and trim of your vehicle to your signature line. That way when you start asking questions in other areas of the forum, we all have a better idea on how to assist you. Click on "Quick Links" above, go down to "User Control Panel" and then click on "Edit your Signature" It'* pretty straight forward from there.