1. Depends on what you're doing with the machine. I have 2GB of Ram and the machine never swaps. You can create a swapfile
if you think you need some swap. Typically I make a swap file 2x the amount of RAM up to a maximum swap size of 512MB.
2. sudo dpkg-reconfigure xserver-xorg
-- If you don't know what graphics card you have, try using the VESA driver.
3. No idea, haven't played much with RAID.