I recently bought a 2008 Edge with 80,000 miles on it BEFORE learning about the PTU issues.
Sufficiently freaked out by all of the horror stories on these things and with the SUV up on ramps I was happy to see that the case was clean and there were no signs of any oil being forced out of the top vent when I inspected it.
I intend to keep it that way, and so these are the steps I have taken so far:
1) I sucked as much of the black, stinky, nasty "oil" out with a hand pump through the unit's fill plug (3/8" ratchet drive) as I could and replaced it with a mixture of 75% 75w-140 gear oil and 25% Mercon V transmission fluid.
2) Drove the vehicle about 50 miles on that mixture.
3) Sucked the thinned mixture out.
4) Removed the heat shield mounted to the transmission torque mount (10mm nuts).
5) Obtained 1/8" and 5/16" cobalt bits and a 9/16" steel bit and proceeded to s-l-o-w-l-y drill out the bottom-center of the case in steps using WD-40 as a cutting lubricant.
6) After drilling through the case I allowed the remaining oil to drain out and sprayed about 1/4 of a can of brake cleaner through the fill hole and then another 1/4 of a can through the newly drilled hole to wash out as much of the drilling debris as possible.
7) Used a 3/8" NPT tap to thread the hole with a 6" extension and a 16mm socket to drive the tap.
Note: Once the tap started to cut I only used 1/2 turns to prevent binding. After each 1/2 turn I backed the tap out, cleaned it off with brake cleaner, sprayed WD40 into the hole to wash out any chips, and then proceeded to thread it back in by hand and make another 1/2 cutting turn.
8) After completing the tapping process I screwed a hex fill plug into my new drain hole and hand pumped as much mineral spirits as I could into the case and let it sit for a couple of hours.
9) Unscrewed the drain plug and let the mineral spirits rush out, washing any of the remaining debris out with it.
10) Sprayed another 1/2 can of brake clean into the case to rinse off any left over mineral spirits out of the case.
11) Refilled case with Royal Purple 75w-140 and closed and cleaned everything up.
I'll drive it around for a while now before rechecking the contamination level, but so far so good.