Yes, bad pinion seal on your Dana 35 rear axle. Easy and cheap to replace if you have a basic socket set and a torque wrench.
I would just make sure the oil is full and drive it. You have two quarts of oil in there. How many days of dripping will it take to leak out 2 quarts? Quite a few days...
Top it off every once and a while and replace it when you get the time
75W-90 gear oil or somewhere close to that will work fine.