hi all

im a novice biker and have recently bought a standard road bike with 21 gears, shimano flick your wrist style. hurts my back when im riding around even though its set to the optimum comfort position. i often find myself with hands in the flat bar position where i have no brakes so an extra thing to think about should a hazard pop out of nowhere.
i want to change this to a flat bar setup, one of those short flat bars that you see couriers using.
as i have a derailleur is this a real pain to do? ideally i would like to swap for flat bar but keep the gears and get those small bmx style brake levers.

can anyone offer some noob style advice? ive browsed the forums but i dont understand the terminology used when describing the procedure. guess im after an idiots guide lol. sorry if this is a dumb post but i need advice before going to the shop so at least i appear to know what im talking about/trying to do.

thanks