you need to find out how much memory your laptop can take first,But i do think you will notice quite a differance if you add more even though your processor is 1.6Ghz
Yes size is important and for all those who say it doesn't, they just don't know because they never have experienced true size. As for your question, if you only have 256mb of RAM, then yes you need to upgrade that quickly...the more RAM the better in my eyes.