Hi mate, VW sell 17" alloys as an accessory for the standard golf and I believe there is no modification required to the suspension (otherwise this would be quoted in the brochure).
The tyre profile you will probably need to look at is 225/45/17 however if you buy a wheel and tyre package, the seller or dealer should supply the correct tyres anyway.
Monzas look ace but I prefer the 18" variety. Not sure what the quality is like on replicas either.
Have a look on
www.rochfordtyres.co.uk , they are dead cheap and have loads of choices including replicas. I bought a set from them once and they are absolutely brilliant. You can even select a car and the correct sizes will be listed on the screen for you.
Hope this helps.
Cheers