Parts list and links at the end.
I originally wanted to attach the goose neck from the handle bars to the seat bar, but I snapped it when I pried it open and tried to close it again. I also drilled a few too many holes in the frame, trying to connect this to that. I didn't go through this with any plan in mind, but a desire to do so.
Parts I used were casters, nuts with bolts, and quick release pins. This set me back about $10 bucks. I also had to buy a $20 dollar rim and a $5 dollar spoke wrench. If you're tires are good you can save $25 or so when doing this.
Tools I used were the typical hand tools, both electric and non powered type. Drills, wrenches; you get the picture.
A big Ahh-HAH! goes to this instructable for the swivel hitch: https://www.instructables.com/id/Bike-Trailer-Hitch-2/
Another big thanks to the guys at my local bicycle shop "Tern of the Wheel" and their website: http://ternofthewheel.com/
A final note: I took it out for a ride. It handled perfectly until I tried a sharp turn at a fast speed. The trailer rolled over. At slower speeds it turns perfectly. The center of gravity is higher and will be even higher after I swap out the wire box for a dog box with two dogs in it. I could add some weights to the axle and/or frame to offset this, but that's just extra weight to pull. I also adjusted my brakes to allow myself to slow down quickly, but not locking up the tires, as I removed the brakes from the rear axle when I removed the gears and chains.