Installing Windows 7 is pretty painless, you may need to get W7 drivers for your motherboard and Graphics Card.
You will need a full version unless you have a previous OS to upgrade from.
If all goes well it should take 15- 20 minutes on that system.
I recomend you choose don't activate after instalation but wait for a few days to make sure all is well. You may as well use up some of the 30 days first.