Yes, the Front Differential has fill and drain ports, both capped with a NPT threaded plug. The plugs have thread sealant on them, don't remember if the FSM said to apply thread sealant to the plugs when putting them back in, I used Permatex Hi-Temp Thread sealant either way. You need a 14mm hex for the fill plug, I think the drain as well, but I forget if its a different size. You need a stubby hex attachment, there is NOT a lot of room for the fill plug, I had to cut the one I got in half with my dremel to get it to fit.
I drained the front on level ground, even poured a few onces of fresh fluid in to purge. When I filled it, I was short a good 8 ounces of the capacity of the diff case. I suspect the case traps that amount of fluid. Next time I plan on jacking up the front of the vehicle after draining, see if I can get the 8 missing ounces to slosh to the back of the diff case and drain.
My gunk was green and grey at the bottom of the rear diff case. Yes, it does appear to be the left over assembly grease washed out and settled to the bottom. The green may have been the grease color, maybe it was something growing in the oil or some contaminant.
When I removed my axle cover, I used Permatex Ultra Black RTV (which was dark grey/mettalic in color, but thats besides the point). The RTV package recommended tightening the pan nuts finger tight and letting the RTV cure for an hour, then torqueing down the pan nuts. I followed the FSM procedures, 2 big ones NOT to miss.
*Clean both surfaces to be sealed thoroughly, Duh
*Apply the RTV bead and assembly the cover to the axle all within 5 minutes, waiting any longer and the RTV will start to cure and will NOT adhere properly to the other surface. (maybe the figure was 3 min, you need to look it up), NOT so Duh, its a good point, and the only times I had RTV leak on me, I did NOT follow that rule.
I did deviate from the FSM, that says to torque the pan bolts right away, I followed the Permatex recommendation to torque them finger tight and wait an hour to torque them down. I figured that would NOT force all the RTV out and let a thin layer cure before torquing it down completely.
I think either way will work fine, finger tight wait an hour, or torque it down completely right away. I think the pan has some divots in the surface to hold the whole surface off the flange. Thus, the pan will NOT force out all the rtv, there will always be some on the surface, or at least on outer edges, that will seal against leaks.
Been 4k miles, no leaks.