1)Am i able to rev the engine to say 5000revs a few times a week without harming engine. (Will get services done every 5000km etc)
Yes you can, they're decent twincam engines and don't mind revving, they sound best over 5000rpm anyway Seriously my car will often see the rev limit, it's governed anyway to a safe level.
2)Looking for some upgrades when I get the car. How much would better suspension set me back.
If you want to do the suspension get a complete handling pack from whiteline...current prices are on their site
3)Would i get any extra KW aftergetting extractors and Exaust installed. How much will i be looking to spend.
Yes you will for sure, cost is open ended really. You can get cheaper exhaust put together or see someone for a full custom job ($2000+)
4)How hard is it to find parts for this car e.g. timing belts, brake pads etc
Very easy, Nissan stock most parts, Nissan NZ are the most helpful though....realistically all places like Supercheap and Autobarn will have what you need, including caliper paint to get those red calipers