I would think that the sun visors would be very similar on all cars, so any guide would likely be helpful to you.. Do you mean the post that goes into the roof or the clip that holds the visor in place (on the drivers side post is on the left and the clip is on the right)?
for the clip:
for the entire visor:
As far as what you can do, assuming you have a jack and jackstands, nearly anyone can do an oil change...
The transmission fluid isn't hard to top up either, just made difficult by GM, but its just untightening a screw and then topping it off until it starts dripping then you're done..
Tail lights are easy on the G6, the headlights are a lil harder but there are guides online..
Brakes on mostly any car are pretty simple, c clamp and some elbow grease (They also sell a tool that helps depress the caliper pistons, not sure if it works on the G6 or not though)
I'd say in my not so professional opinion, that anything which shouldn't require a lift or specialized tools like rotor resurfacers or tire mounting machines, you should be fine to give a quick google search or a post on here (Thats what brought me here -- questions!) and you should be fine.. I really like my G6, bought it last month