I have heard mb rotors should not be turned....
I replaced mine for cheap, like $120.00 for the whole front. that was discs, pads, stop squeak and abs sensors...
discs were like $35.00 each I think. Ordered right from partsshop on this site.
As long as the discs are coming off I say buy new ones, cause the labor work is already there.
If there is no noticeable lip on the edge of the rotor, the discs should be fine. if there is a lip, I would suggest replacing them. I had discs with a lip eat through a set of pads in less than 10k miles.
'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.