The socket really helps but it's expensive if you are only going to use it once, I bought a craftsman socket and had cut it in half. I cut down a piece of tubing the depth I needed and welded it between the two halves, this is pretty easy as long as you have a welder at home and the supplies readily available.
Have you tried putting heat to the nut? I'm scared to ask how you are holding the shaft when breaking the nut loose? I ended up cutting mine off before I had the socket but if you are going to attempt this you must be VERY CAREFULL not to touch the shaft or threads with the cutoff wheel. A bit of antisieze helps for reinstallation.