You'll need a 14mm hex socket (found at most auto parts stores -- got mine at Autozone) and a nice long socket for good leverage.
If the bolts haven't been removed in awhile they'll be pretty tough to get out. With the car jacked up, get underneath there and use your foot for more strength if you have to. USE A JACKSTAND! That's how hard it was for me to loosen those large hex bolts, although mine was being changed for the 1st time at 198k miles
Get some 90w diff fluid. It took a little over 1.5 quarts to fill my 300E. Also, a pump is recommended to get the fluid up into the hole as there's little room to work up there where the fill hole is located. Pump was $5 at O'Reilly's, and it screws onto the top of the lube containers.