Easy to change, just unscrew the old one and (carefully!) screw on the new one nice and tight. Would be quite expensive and you'd possibly be better saving up for a 4.5k system instead.
As for the need to change how much paint do you shoot?
If your a floor chewing front player who only does 500 paint max then you'll probably be fine. If your an 18 pots a game back player then you'll be wanting a big 4.5k system.
I've read good reviews on the nitro duck systems but you should seriously think about a higher pressure system. 4500 psi is the norm now.
hope this helps
Laterz
Ian