Clark - First, there are two books you must read...one old and one new. Don't NOT read them. You'll thank me when you do. The first is "Elements of Effort" by John Jerome. When Jerome died a few years ago the New York Times obit called him the Best Writer Nobody Knew. I agree with that. "Elements" a bunch of anecdotal peices about running that will teach you, delight you, spur you on.
The second, just out, is "Born to Run" by Christopher McDougall. Don't be put off by the simplicity and pedestrian (no pun intended) nature of the title. This book, I predict, will be a classic and a best seller. It's about running in the extreme, for sure. It's also about new findings and new thinking in the discipline (running is far more than a sport). It's also, about life and what it means to be human. "Born" will introduce you to some of the most delightful and unimaginable characters you've ever encountered.
Before I get to your specifiic question, let me establish my credentials. I've been running for over thirty years...probaby over 60,000 miles. I'm a veteran of 25 marathons with a personal best of 3:08 when I was forty, and 4 fifty mile ultra marathons.
Now, to your questions. You will probably only ever "love to run" on occasion. I think most veterans will tell you that. What you will find is that you'll get to the point where you can't not do it. And that where you want to be. Being a dedicated and disciplined long distant runner will simply change your life. It will make you healthier...physically, mentally and emontionally. It will put you in touch with like minded people who will both nourish you and give you sustenance. It will, better than anything I know, put you in touch with you body and, as a result, your mind and spirit, as well.
Regarding your questions about sprinting on concrete...no, it won't hurt your knees. But rather than elaborate on that, I, again, urge you to read "Born to Run." The big answer to your question found there will surprise you. Why, by the way, would you want to sprint anywhere at this point?
And about earphones and all the other gadgetry...ditch then. Ditch them and pay attention. Listen to your body, watch your surroundings, meditate on the run. You don't need Morning Edition or the Hit Parade to be a runner. In fact, they are an impediment.
Hope this has been helpful.