Homelink in visor
The newer GM vehicles don't come with Homelink systems. I converted mine, so it would work with my "mild to wild" exhaust system, instead of the remotes that come with the kit (for the dual mode V systems). The mild to wild systems are not compatible with the newer GM system, as well as some of the newer garage door openers.
In order to do this, you have to crack the visor (literally - they are epoxied together), and replace the unit) module with a "Homelink" module. You can buy these as separate units, or get a donor visor to do this. They are plug and play, to the same connector inside the visor, and the same dimension. click it back together and epoxy shut and you have "Homelink". Make sure you get the units with the rolling codes capability - made after 2001, if you want to use it with your garage door opener that uses this technology.
Now, I have easy access to the "wife" setting (mild), and the "husband" setting (wild), without having to fumble for the remote fob.
If you do not feel comfortable doing this yourself, you can take the module to your local auto upholstery shop and they will do it for you for about $25.
The answers to getting that plastic cover off are addressed well, in the previous posts - pry and slide from the inside. This exposes the mounting screws and you pull the unit out and plug the unit back in to the connector tucked inside the upper pillar.
Hope this helps someone...
Do I slide it up or down?
You have been very helpful to me and I will also try to help you be doing research for a left sun visor with a home link. Please tell me what color you need.