Updating an old Mac for Plex

Hi everybody,

So I have a MacBook Pro from 2008 that I turned into a Plex Server. For most of my usage it works fine, but when I use the computer to add new movies and stuff it's reaaaally slow. I'm also afraid it's a bit too slow for transcoding fine.

I'd like to know if you have any idea of what material composants I should upgrade so that I have a nice working Plex server that can transcode, be accessed through Screen Sharing, and even sync with Dropbox all at the same time.

Here's the configuration :
MacBook Pro 15" 2008
OS X 10.11.3
2.4 GHz Intel Core 2 Duo
2Gb 1067 MHz DDR3
NVIDIA GeForce 9600M GT 256 Mo

Thanks for your help !