I heartily agree with the 'normal' state of oil seepage from the differential, but if you want to do the seal(s), the pinion is the scary one, for me anyway. There's a 'black magic' setting of the pinion to gear which is disturbed and must be re-set to change this seal. The axle seals are easier, as I understand it, but you'll need to remove the respective axle to change the seal.
Both my babies weep gear oil. On the SL, the car is new to me so I have no idea how long the seepage has been there. My plan is to clean it all up (done), check the oil level, change the oil, then watch the situation. Maybe an additive to help the seal might be a good idea if it persists.
My now retired indy once mentioned to me that 'they all leak there', and that's after over 30 years servicing Mercedes. He would enjoy fixing this for a customer of cour$e, but for me, I got the distinct impression that the job didn't justify the seriousness of the problem. I live with it on the SE.

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1986 560SL
2002 Toyota Camry
1993 Lexus