@Internomad, looks like you're getting great advice and you can see the community is a big support.
If there were one nugget I would give you to start it would be to go slow. This game doesn't just come to anyone, they have to get it by trial and error. I have played since GT first came out and hours and hours of driving slow cars, reading about real racing techniques and doing License Tests until they are all Gold really got my foot in the door.
Every itteration of GT that comes out I do the same thing.... License Tests First/All Gold. I did not do that with GT5 yet because my patience ran thin this time! Maybe why I don't play GT5 as much as I used to play the others in the series. From what I can tell this really is built for the racer that has a good Wheel and Pedals and really leans on the competitive online aspect.
I've always been stuck to playing with friends and family locally and the adjustment is not easy. You'll find Bruno the Bruiser on every public lobby you join and be ready to be scolded by every pro GT driver out there when online.
Ok, no more grumpy guss here... Awesome game and you made a good choice going with GT5