Bumping for visibility... First, you can fill it from the top with a funnel with a long flexible hose, the built in one is worthless at this point, but that would be the easiest fill and maybe worth a cheapie hose funnel thing...
Update on doing this at 12k with the 2L and now at 18.5k: 99% of gearbox issues are resolved, first just likes a bit of a warm up or will shift a little hard the very first time when cold, but that's it. All gear whine, missed gears and general "crunchiness" are all gone. This could be because of 2 full liters vs. 1.67, because the trans needs to fully break in, the fluid itself, or some combo of the three. But regardless, definitely recommend this after seeing the grey watery crap that drained out. When I saw that I thought "Damn, I wish I did this even sooner..."