You'd be surprised, Mrs SB is not a natural runner and never thought she could run and completed 2 Half marathons, she started of by run/walking and ran a 5k for sport relief and it went from there.
If you have not really run and would like to run the whole way then a Walk/Run training plan is a good idea. I successfully got my sister running a mile with this technique. It gets you gradually used to running and helps avoid any injuries through overdoing it. It also provides structure and focus something I always need with training for big runs/races.
Before you start walk/run training plan it is best to make sure you can walk at least a mile or so,
Have a look at these training plans
http://www.runnersworld.com/getting-started/the-8-week-beginners-program
http://www.bupa.co.uk/running/training/training-programmes/beginner-5km/
As for outfit, head to sportssoccer get some cheap running tights/leggings they'll keep you comfy and a run tshirt too these help wick away sweat from your skin, there always sales of karimoor stuff so you can get it cheaply and a comfy pair of running trainers (that you don't mind getting muddy)
Runners high? Hmmmmm best way to describe it it's like a huge release of adrenaline - I get it after a hard run or treadmill session and the end of a race like a Race for Life type thing, it can occur in any exercise not just running its a release of Endorphins. You feel energised and excited.
You will definitely feel a huge sense of achievement doing it and there is a lovely camaraderie too - I have marshalled Race for Life events in past they really are a fun thing to do.
You are giving something challenging a go and that is a great thing to do, I will not forget to sponsor you
