You don't need a damper if you're suspension is in proper order. Other than that it's putting a Band-Aid on a shark bite.
Any shock through 2011 will mount up, to make things easier use the dogbone that matches your shock. They add adjustability and aren't as stiffly sprung from Kawi.
The 07/08 swingarm is stiffer, without being as stiff as the 05/06 unit, and can be found for cheap and is another easy swap, pair it with the rear brake setup to increase the benefits.
Fork internals are a good upgrade, but you can swap forks through 2008.
07+ front brakes (the black Nissin Calipers) are a direct swap, you can upgrade the rotors as well but will need spacers on the caliper mount if using the 03/04 forks.
The best thing you can do is make sure the bike is tuned up first, a fresh set of plugs and a throttle body sync while checking the valve clearances (unless done recently with documentation) is going to be a good starting point, and shouldn't cost more than about $300-$350 at a dealer if you aren't up to the task. As with anything approaching 10 years old the maintenance things should be checked first, especially since these bikes are popular with the stunting crowd.
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