Removing blacktop/asphalt pad
As i get older and less ambitious to tackle tough jobs like your facing by hand, I take a little trip to my friendly "Rent Me" store for my favorite little Kabota backhoe/loader. Half day rates here are about $65 and I can do more in 2 or 3 hours with a good tractor than 2 men can do in a day by hand, and my back feels great afterwards!  lol The other nice thing about using a little loader is that you can easily transport or load your spoils, and if you have your new material handy, you can move that around also. How do you intend to dispose of the old asphalt and gravel?  You may also consider making a few calls to small excavation contractors in the area. you may be able to hire a machine with operator  and a truck to haul it all away for $70 to $100 an hour. A job that size would only take a couple of hours and the spoils would be gone as well.