That does not look wet but does show dry seepage. Is likely ok but the fill plug is a 3/8" drive that can be removed and use 75w-90 gear oil and squeeze some in there, on flat ground. When starts to come back out, is full. Usually, the 75w-90 container has a pointed snout that the tip gets cut off of and unscrew the cap and remove the seal. The tip will have a removeable small cap to put back on when done squirting in there. Looks like very slight pinion seal seepage and slight diff cover seepage. Kinda normal at that age.