You pretty much have it. The 'N' wireless isn't needed for your uses, except that it offers better range, this is the only reason I have a "N" router. I run "G" cards in all my PC's and the router set for B&G only. I get great reception through out my house with the 'N' router. My old wrt54G router just didn't have the range to reach the 2nd floor from the basement nor a corner of the kitchen, even with booster antennas. You should be up and streaming pictures in no time.
Just follow the installation instructions for both and you should be fine, it isn't hard to set them up. Once it is working or at least arrives, post up what ever questions you may have.
