I believe that one will test the truck side circuits but not the actual trailer. Looks like the brake tester is testing the adjustable brake force signal from your brake controller.
Here is the one to test the trailer...
I kind of like the know shifter in my Ram vs the console shifter in my brothers Ford. Its all electronic shifting and I would much rather have the extra space in the console. Only frustration is the truck I drive at work has a column mounted shifter so I am always reaching for the wrong spot...
As others have stated its based on the year it is sold not manufactured. This is why when you get parts for tractors and other equipment such as mowers they ask for the serial number and not the year model as they track the parts compatibility by serial number sequence.
Depending how much land you need to remove rocks from you may be better off hiring someone with a rock hound attachment on a skid steer or possibly renting one if a local place has it available.
Its not a problem if you do it correctly. Fill the tank with water to displace any remaining propane and you can cut it without issue. Have seen several done this way to make trailer grills etc