I did the Ring in April this year. I used a GTI from Rent Race Car, they are fantastic. It is an expensive exercise, so be realistic and don't think you can do it cheaply.

If you can time it for a public holiday (when the ring is open), that would be good as it will be half as busy as a normal Saturday/Sunday.

Read all the ring sites before you go (Ben Lovejoy's site, etc) and make sure you have some travel insurance with rental car excess behind you...just in case.

I would spend some time on playstation, xbox, but it DOES NOT equip you to take on the real thing.

Last, but not least. You are the slowest on the track, everything (and I mean EVERYTHING) is faster than you, so just have fun.