Make sure your 4Runner has the frame mounted hitch and not just the standard one that mounts to the x-member. The frame mount can handle a WD hitch, the other won't and risks frame damage.
The T4R is a great vehicle (I've had 2) but the short wheelbase is not ideal and can lead to sway issues. Get a proper hitch with built in sway control like the Equil-i-zer or Reese dual cam at minimum. If you have the rear air suspension you want to turn it off when hitching up until the hitch is adjusted and tensioned, then turn it back on.
You may want to consider upgrading tires too. The stock P rated tires are soft and squishy.