I towed one 400 miles with my Suburban a couple of months ago. It had surge brakes and worked OK. I used a U-Haul ball mount with a slight drop. I think the 4Runner receiver is slightly higher off the ground than Suburban's, but it's not here right now for me to check. The Toyota ball mount in the recommended "up" position might be slightly high, but might work. I've also used the U-Haul brand ball mount in the 4Runner receiver (it fit fine), so you could buy one on the spot if you had to.
You'll also need a 4 pin converter for the trailer lights. I can't recall whether or not one comes with 4Runner.
I think you'll find the rig will tow OK. In my experience, UHaul trailers are adequately maintained, but just barely. I can't say the same for last UHaul truck I rented.