Contrary to what people are saying, the core 2 duo still has at least 2 more years of life in it even with core i3 coming out. Intel may stop making chips for that exact sku but it doesnt mean that the processor is useless. I am ekeing out the most out of my e7500, and before that I did so with the e4600, if you buy at least the e 7400, or the e7500 now, you will not regret it.
First thing first, chech out if your motherboard can even use a core 2 duo of this level.
If so, then you will have no problem. Seeing as your mb can only hold 2GB MAX? Then I doubt you can use your motherboard. If so, you should think hard if you wantto buy a really decent LGA775 or go AMD since they are cheaper and get an AMD processor. If you do have a budget, this or a new LGA775 such as the asus 5pq or an intelX45. FOr AMD asus m4a785td is decent at $100. Then you can get processors at around $80-200 for these boards that will last you for a while.
If you dont have a budget then just get an X58 all together and you will use that for a long long time. It will still be decent in 5-7years from now. It just costs alot more.