yeah get at least another gig of ram, it doesnt cost much nowa days now that DDR2 ram is out.
For finding out what ram you need go to crucial.com, theres an online scanner that will tell you exactly what you have now and how many slots you have
Secondly what graphics do you have now? the guy above is assuming its an agp card, he's probably right judging by your machine but its worth double checking.