I think most of the specs were between 40 and 60 ft/lbs of torque... I think I went up to ~70-80ft/lbs for most of the larger bolts... I didn't want to go tooooo far, but I think if you went until they were pretty tight and didn't try to go beyond that, you should be fine.
I also peeled the center 'hidden hitch' sticker off of mine before I installed it. Looks much more clean (OEM/factory) that way.
Taking the rear bumper off wasn't nearly as big of a job as I had originally thought it would be. I only had one of the little plastic 'buttons' break on me when I tried to take it out. It was one of the little plastic plugs that is on the inside of the hatch on one of the sides where the bumper and hatch meet each other when it closes... I have never bothered to get another one, as I put it back in and have never noticed it since.
I'm surprised you were able to still find the 70411 hitch. I really want to know why they ended up discontinuing that hitch because it's so much nicer than the newer ones they have that require trimming of the rear bumper cover, and the newer ones also aren't designed for 5,000lbs weight-carrying. Also, that's steal of a price you got. I think mine was around $120 or so from e-trailer.com (of which none of these places stock that hitch any more).
Ricky