Seeing the seams line up in such a small area is what will make the patch look obvious. Aluminum siding is put together in such a way that you can't remove a piece out of the middle. The bottom row is the first to go on and each row is locked into the row below it and then nailed at the top. This could be a very big job depending on how long your wall is. You will need to start at the top, remove the finish piece (it will probably be bent by the time you are done) and remove row by row till you get to the one below your window. You have to be careful removing the nails and the aluminum can bend pretty easily when tapping it and trying to unlock one row from another. I suggest two people, one on each end of the piece. If you get this far and still haven't pulled all your hair out, the rest will be pretty easy. Make sure you stagger the seams. Be careful not to cut yourself.