REPORT CARD, Is it something serious??

[frankbenz]

I just took my 97 E420 to the dealer for a 4 wheel alignment and as usual they wanted me to change or service so many things like sparkplug, differential oil, etc., etc.
But the most concern was when they tell me that there’s a REAR DIFFERENTIAL LEAK FROM SIDE SEALS and quote me $585 p&l., FT (front ?) FLEX DISC STARTING CRACKED and VEHICLE BELLY PAN MISSING

So what was that all, and is it something DIY ?
Any inputs appreciated, thanks in advance

frank
97 E420 132K