Currently Being ModeratedAug 5, 2011 7:13 PM (in response to Holdstrong)
You can actually go up to 6GB (4+2), but yes, 2+2 for 4 will work.
It's 200 pin, PC2-5300 667MHz DDR2 SO-DIMM. Try Kingston, or Crucial or Macsales and you'll be able to look up the correct RAM by your machine type (it appears to be an early 2008 15" model, based on what you've provided).
Yes, I believe it is worth it. I have the same model in a 2.5GHz, and have no plans to upgrade at this time. Would I like a new quad core i7 with 16GB RAM? Well sure, as long as it's on somebody else's dime. If money is no object to you, go for it all and forget about upgrading RAM on this machine.
I would also recommend spending another $29 or less and upgrading to Snow Leopard (10.6).