For a 2 ton camping trailer your U.S. hitch setup will likely include a 2" receiver hole, a 1" hole for the trailer ball stem, and a 2-5/16" trailer ball. If you prefer to comply with a max 11" tow bar, you might consider the 10.5" Draw-Tite #40343, #40382 or #40443. I forget what max rise is listed on the factory Westfalia hitch label, but if you need an 11" tow bar with extra rise (your rig looks like a sagging "V" in the middle when viewed from the side in spite of the air suspension), you might try the Reese #21345, Curt #45230, Brophy #BM40 or #EA40, or Draw-Tite #40345 or #40382. Trailer ball nuts can loosen over time even with a lock washer, so I chose to double-nut mine, although a Loctite threadlocker might work too.
-Regarding "84% new trans fluid," each drain and refill will retain 40% of the old fluid. So a SECOND drain should retain 40% of the previous 40% old fluid, or 16%. And 100% - 16% = 84% new fluid. A third drain would result in 93% new fluid.
-References to adding a trans cooler to an L322 refer to a SUPPLEMENTAL or alternative cooler since 2003-2009 L322s came with the small, occasionally overtaxed (towing) factory trans cooler under the engine radiator.
-The bottom eight rows of the engine radiator supply coolant to the trans cooler, so if there's a coolant shortcoming with the trans cooler, it could be caused by corrosion/blockage in the cooler OR radiator.
-The purpose of the trans cooling mode is to limit the drivetrain to gears 1 through 3, and therefore move higher flows of both coolant and trans fluid through the cooler until the trans temp drops below 266 F. The mode also alters torque converter lock-up mapping, reducing heat associated with slip.
-If your shop prefers BG chemicals for sake of convenience (not uncommon), their "BG Premium Full Synthetic" trans fluid meets the LT71141 spec and works fine, one of a number of appropriate fluid brands. See other threads.
-Per Robison Service, a large Rover shop, all of the L322 BMW cooling system components are suspect by 100,000 miles, with preventive replacement often appropriate.
-For my L322 there's no visual or audible warnings for trans cooling mode -- you'll know when it revs high. It seems that the more serious "Trans Overheat" visual may not go away until you restart the engine, even if the trans has cooled back to normal.
-Ditch that idiotic, old-school block of wood under your trailer jack with a Husky Brute Super Foot or Fastway Flip.
-Reese sells kits with all three hitch locks conveniently keyed alike, occasionally on sale at auto stores.
-The owner's manual suggests that proper towing tire pressures may be 36 psi front, 44 psi rear.
-"Walgreens Rinse Free Body Wash" is a great, residue free product I've used when you can't shower in your RV.