You just may have to go outside of your immediate area to find one.
Any ditchwitch will make somewhat of a mess. I rented a big one and dug a 800 foot water line. Fun job.
Or just go to HD and hire a couple of day laborers to dig it for you.
Probably cheaper than renting equipment and easier...
Dirt lasts forever, which is what you have basically made. If you go to a nursery and buy a bag of compost, this is what it is.
Yes, you can keep adding to it. Throw in your garden spot a month before you are ready to plant and till it in.
There are numerous ways to create compost piles.
The most important is to try to shred everything up as small as you can and you have to keep it mixed up. Leaves need to be shredded. In your trash can method just rolling it around on the ground will help. Keep it moist, not real wet. It has to...