You can obtain the heat sinks and CPU tray for approx $700, plus two new CPUs which will cost you over $3,000 for the 3.3 GHz variant. You don't need new RAM, you can use the RAM from your quad.
Still, you're looking at over $3,500 (conservative) to convert your 2009 Quad to a 3.3 GHz 8-core. Financially the upgrade doesn't make much sense, especially since we will most likely have 6-core and 12-core Mac Pros in 2-4 months.