On a MacBook Pro, you can only upgrade the memory and the hard drive. Other hardware is soldered into the logic board.
Respecting to memory, Mid 2009 MacBooks Pro can run 8 GB of memory (evidently, 2 GB aren't enough, more if you are running Mountain Lion). You can buy more memory in OWC or Crucial > http://eshop.macsales.com/shop/memory/Apple_MacBook_MacBook_Pro/Upgrade/DDR3
Respecting to the hard drive, you can install a 7200 rpm hard drive or a SSD in order to improve performance. You can buy a hard drive and you have the steps to do that in OWC > http://eshop.macsales.com/shop/hard-drives/2.5-Notebook/ If you can afford a SSD drive, go for it
Currently Being ModeratedMay 2, 2013 5:31 AM (in response to Pro Apple User)
Pro Apple User, greetings; The only difference that Apple RAM has compared to OWC or Crucial RAM is that it is more expensive and thus adds to Apples cash hoard.
From a functional standpoint there is no difference. Mende1 is correct.