A Tacoma v6 is a much better tow vehicle than a Highlander, especially if said Tacoma has the 2" reciever and 7-blade RV connector already in place. You'll need an electric brake controller (I like the better Tekonsha models like the prodigy P3, and they have adapter cables that plug and play for most every major brand of tow vehicle, including Toyota). I'm 6' tall and found that I had to trim the Tekonsha brake controller mount down some to mount the controller as close to the bottom of the dash as I could so my knees didn't bang it. YOu want this controller mounted where you can reach it with one hand in an emergency to engage the trailer brakes manually. I've only had to do this once, and it was a life saver. With a Tacoma 4x4, you'll want a 2" tow bar ('ball mount') with a 2" drop and a 2" ball rated for a 7500 lb trailer to have nice safe margins. I like getting the slightly longer than normal Curt 45260 ball mount as it ensures the tailgate *will* clear the trailer's jack. If your Tacoma is NOT a 4x4 (or Prerunner), it may not be adequately tow rated.
for water and sanitation, I would have TWO hoses, one white drinking water approved hose, and one generic green/brown/whatever hose for hooking up at dumpsites that don't already have a hose, and I would have a pair of heavy duty rubber gloves for dealing with Mr Sewer.
IF you have an oven, I would have a nice heavy gauge aluminum quarter sheet pan for baking, and a roll of aluminum foil for covering it to make cleanup easy. bare minimum of cooking pots, just enough silverware, non breakable plates, glasses for you and your travel companion(s).
mattress pad and fitted sheet sized to the supplied mattress ('Full XL' for a Classic 21, thats an odd size but you can find them), and a quilt stuffed into a duvet cover a size larger than the bed (queen for the 21 Classic). 2 pillows w/ cases in your preferred style/size.
Whatever it is you use to make coffee without electricity. In my case, thats a small kettle for boiling water, a Melitta #4 'one cup' filter holder and filters, ground coffee or a manual grinder and whole beans, and a couple mugs. If you don't drink coffee, well, ignore this.
I would suggest a small folding table, and 2 comfortable folding chairs, suitable for hanging around outside your camp when you're just chilling.