First, just because it's fairly rare to see a 28 year old guy buy his first skateboard, I gotta ask why you bought one.
On the turning, if you aren't having problems turning right, and riding regular, then there's a good chance that you are psychologically intimidated about turning towards your darkside. Your trucks could also be too tight, but that's unlikely if you don't have a problem turning right. Did you get a professional to set up your deck for you?
There's also an off chance that you could actually be goofy footed. Do you wakeboard or snowboard? Have you done the backwards push test?
As far as foot placement goes, shoulder-width or so apart is the best for stability. You want to bend your knees just a little bit to lower your center of gravity and absorb shocks in the road. You are also more stable if you lean forward (in the direction you are going) slightly. Try to keep your body as parallel and balanced as possible over the board. Your hips should initiate your turns and generate most of the motion, while your lower legs and toes fine tune your movement.
Since you're new, you should also use your arms for balance. Pick them up til they're about level with your abs, not much higher.
If it feels natural and balanced, you're doing it right!
Other tips:
It helps to have skate shoes for grip and also to tear up. If you get going too fast for comfort, you can drag the sole of your back shoe to check your speed. If you're going too fast for that, try to bail on the softest thing possible. Grass is much better to crash out on than asphalt or concrete.
Never fight a fall, try to roll with it and spread the force through your body. Be especially careful with your ankles and wrists. While they are both rather painful/disabling, wrist sprains take FOREVER to heal, and become very easy to re-aggravate.
Protect your head. I wear a helmet, I don't give a damn if anyone else thinks it's dorky. My little cousin had his head run over by a pickup and died last month (non-skateboard related). Traumatic brain injuries are not DJ.
