Sometimes you have to jump in and just do things no fear.

I replaced my diff in my w210 but at 518k it was pretty worm out. Mostly from the P.O. running it low on oil and a nasty whine which eventually lead to the diff locking up at 5mph and me buying it for $250

Differentials aren't as scary as one would lead you to believe. I've assisted in rebuilding one on a jeep, but the principle is the same. If you decide to do it, I can help as far as questions go with any issues even though you're not rebuilding yours but resealing.