Hydration: don't worry so much about taking water with you when you run (most beginners do). Hydration is omething you need to be doing all the time. Literally have water with you all day and take some every 20 minutes. Many different parts of your body will store the water.
Healthy running: follow a program and keep a note of your runs. Observe rest days (you can still play golf and what have you). If you feel a niggling injury beginning, take some time to rest and stretch out that body part. Look up some stretches and do them religiously within 20 minutes of finishing your run. Stay safe when running on the roads: buy an item of clothing that is flourescent yellow.
Find a pair of pants that stops you from getting chafed (you will be surprised how painfully this can be!).
Count calories: work out how many your runs are burning. That way, you'll resist the urge to reward yourself with too many treats that you've 'earned' through running. At the same time, recognise that you need some good quality carbohydrates - or at the very least, protein - to keep you fuelled as a runner.
7 1/2 stone is like carrying a second person, so well done on the weight loss.