to remane a file just ckick once on the file name, wait half a second, click once again and the name should become highlighted, then type in the new file name.
for organizing pictures iPhoto works decently enough. drag you photos into the library window, let them load, then select a subset that are related and create a new folder for them in the sidebar.
There are other programs out there but I don't have any experience with them or remember their names offhand.