regards to draining the system, there is allegedly a drain tap on the bottom hose of the radiator.
if you can find it this is the best way to drain the system or remove the bottom hose (you'll have to jack the car up to do this)
NB anti-freeze is an irritant and toxic it will f**k your paint up too
also if you going to use anit freeze that you have to mix make sure you do it with deionized water, the golf takes about 3 liters to fill the system.
when you come to fill the system, fill the expansion tank give the hoses a squeeze as this gets the air out, top up the expansion tank (rinse and repeat till you're at the fill level)
run the car till the radiator fan kicks in (on the drive) leave on idle till the fan cuts out, leave the engine to cool, top up system
keep an eye on the dash though as if you don't have enough in the "STOP" warning will come up.