I would recommend to have 512 MB of ram (or more, ram is getting cheap these days). Make sure that the ram you are getting is optimal for your motherboard, so it doesn't become major bottleneck. I would recommend keeping a backup of all your important files, be it on a secondary hard drive or dvdr. Also, to have a quieter computer, I would go with aftermarket cpu cooler (don't forget to put thermal paste in between, Arctic Silver is one of the good ones).
Some of the coolers that come to mind are from Thermaltake, Zalman, Arctic Cooling and Scythe (my favorite Scythe Ninja Plus). Add to this nice and quiet Seasonic power supply and you are in business. Computer case ... well, I can go for hours on this, but that all depends on the amount of money you want to spend on this (that you haven't told us about to make it easier). All I can tell you that it's worth it in the long term, as you can upgrade the mobo later on with another cpu and memory and perhaps video card while all other components can be reused, including the cpu cooler. For added quietness get an older video card that has no fan, just a heatsink or add aftermarket video card cooler with larger fan.