MaraudeRS, my bike is 6 years older than yours.. 61,000 miles when I got it. Had been sitting for 9 years but corrosion free....just dusty. My brakes were fine. Replaced pads...EBC organic, if memory serves. Showed my brake lines to a bike mechanic. Original units with the little date bands on them. He said they were fine and have been for almost 2 years. You can polish and paint those engine casings if you so choose. I would do the frame myself. No need to pay a pro for that unless you want something funky. As was mentioned you will likely find that the various components improve with use. I had a leaky rear brake cylinder. It stopped leaking. The engine tended to get smoother and happier the more I rode it.
One more thing, in my humble o. Don't worry so much about cost (within reason). You are resurrecting not just any old motorbike rather a piece of motorcycle history....and a fine German marque at that. I'm no BMW snob but do a little research on the history of this thing and your appreciation for what you have will increase. It's not an investment. It's a labour of love. At the end of it you will have a unique, slightly odd-looking, fun and reliable companion that will take you way over 100,000 miles. I've got a Kawasaki Concours (same format as my RT) that is a fine machine. But I just had to get a Brick for that whacky engine and all the other weird features that BMWs have.
You've heard it before but I'll say it again. Don't take two wheels for granted. Things can get out of hand in a hurry on a bike and that's just on your own. Throw cars into the equation and the risk level spikes considerably. Take the training. Start small (you can always sell off a small bike), really feel what the machine is doing and take things slow!! Speed and poor road surfaces (oil, gravel, sand, black ice) will take you down. Having said that there is nothing quite like motorcycling. Once you love it you love it for life. Make sure you live to ride another day!
One more little hint...if you go to replace the rear brake rotor the manufacturer apparently used permanent (red ?) Loctite on those bolts. They need to be heated up to remove them without stripping out the head....this according to the foul-mouthed but beloved Beemer mechanic, Chris Harris (Affordable Beemer Services). You've gotta view his stuff!
Good luck!