I'm completely new to the world of moded cars and cars in general. What simple tune up's can be done to the G8's L76 to increase performance and what exactly are tune up's?

Start with one of the intakes spoken about on the forum, little exhaust and vms tune. You are good to go.

Tune Up is really a term from 30 years ago, when cars needed spark plugs replaced every 30,000 miles, points changed, Carburetors adjusted, etc. On a modern car, there is nothing to tune-up. Plugs are good for 100k miles and everything else is controlled by computer and doesn't need maintenance.

To increase performance:
Cat Back Exhaust
Headers
Cold Air Intake
PCM Reprogram for use with premium fuel.
And don't forget for every Flowmaster, MSD, K&N, or Holley STICKER you put on your car, each is good for additional 5 horsepower. Unless you combine them with the Performance "CHIPS" sold on e-bay, then you get 10hp per sticker. However please subtract 2 hp if you are using a fuel magnet to increase Gas Mileage.

I know what cold air intake is but what is PCM reprogram? How do you do that? What are headers?

We offer that, check out our website or the other posts in the Tuning section for details :) It's the biggest change for the money you can make to these cars right now!