RAM upgrade Acer Aspire 5742

Hi! I have an Acer Aspire 5742 series laptop and wonder if upgrading my current 4GB of RAM to an 8GB is worth it? I sometimes do photo editing in Photoshop and video editing in Premiere. Would that give a performance increase in it?
Also, is it possible for me to replace the CPU? It currently has a Core i3 380M and from what I've seen in the website, a variation of it can support the Core i5 4xx and 5xx CPUs.

http://support.acer.com/acerpanam/notebook/2010/Acer/As...