Your solution sounds like it will work, but you might also check with your local utility company on rebates and stuff like that. A lot of times they are running special promotions and you can get some money back anyway to help.
And Teacherbailey is quite right all an AC unit puts out is hot air! It's a sealed system and keeps the coolant inside. Since light isn't an issue with you, blocking the window off will probably give you the most bang for the buck. In the South they tell you to keep the blinds closed during the hot part of the day and not to open up until it cools off. Still couldn't live here without AC, as far as I am concerned.