The oil filter is located underneath, on the passinger side. It's a good idea to put your car on ramps to change the oil.
As to what oil to use, it's more a question of what you are doing with the car. Thinner oil is a little better in cold weather, but it doesn't work as well in hot weather. 5w 30 is already pretty thin. Thicker oil is better if you drive the car hard, but thinner is fine if you drive normal.