Yep, most of the plug n play wiring harnesses terminate in a flat 4 connector... BUT, there are any number of 7 blade receptacles that come with a pre-wired flat four pigtail, so all you have to do is connect the two, add the brake and charge lines, and you are good to go.
At least in FGRV's your vehicle can tow, there are only two hitch ball sizes, 1 7/8" and 2". As a WAG, most are the 2" variety, just verify with the seller. As a temporary solution there are multi-size drawbars, with two or three balls attached, available. Check with Harbor Freight for an inexpensive one. Adjustable hitches are expensive, and all are guaranteed to meet up with your shins when installed. Again, if you start with the standard height for a
Scamp, you should be fairly close for starters.
And Jon's advice is pertinent. Unless it's a super deal, I would suggest just avoiding any that don't have
brakes from the get-go, as well as any that look like they will need a new
axle. But aged
tires are always a concern, just check the numbers as it's not uncommon to find aged out
tires, especially on rigs that haven't been used for several years.
Good luck with your hunt