OK ... installed it and took a little over 2 hours ... was really taking my time to make sure I didn't break off clips or strip bolts, etc. I did not use an electric driver as I was sure I'd get one of those cross-threaded screws (and there were 2) ... carefully hand unloosening with ratchet worked well ... I'm pretty handy and have done this on several non-tesla vehicles (X5, Volt, ES350) ... this one seemed to be the most challenging for a few reasons:
1) My tail lights were recently re-aligned by service center to fix gapping, so I was super careful to mark with tape where they lined up before removing.
2) Space to work with tail light nuts was super tight ... I really try to unclip as little as possible, but was tempted to pull more of side panels away to do the job but figured if I'd do that it would end up creating all kind of interior rattling after popping back in. Not a lot of slack on the wires ... need some small hands to unlatch/latch connector.
3) Seating the bumper cover by myself was a pain (get a 2nd set of hands)
I'm sorta happy with the result ... yes I saved $700 ... but not real keen on the error messages that pop up while driving (see pic) ... it comes up more than I'd prefer and a pain to clear. Hopefully they will release a bike/cargo rack mode to disable rear sensors. There have been times which AP was choking when I tried to enable with that error message displayed. It finally does, but has seemed flaky.
Access panel thing is not really ideal ... I see myself breaking off clips after a year. Actually thought I had cracked off rim of bumper cover on the right side when I took it off the first time ... was REALLY happy to see pictures here that showed the same gap in the rim. I'm debating whether to come up with some spring mechanism for it like the old cars that were fed gas from behind the license plate.
On a good note, I have a cheap Swagman double rack that's worked rather well for me over the last 5 years and the lift gate clears it when folded up! (by about 1/2")