For pads, just use the "yellow box" Textars if possible. These are the OE pad on European models. Standard Textar, Pagid, or Jurid pads are also good and are OEM for the dealer pads.
Squealing is rarely a problem with the pad or compound. It's a problem with the person who installed it. You need to use high-temp brake paste on all metal to metal contact points between pad and caliper (pad backing, edges, etc). Do this properly and you'll be squeal-free. The OE stuff comes in little packets for about a buck. DO NOT use the garbage from McParts (Permatex, etc) as this junk hardens up and is like RTV - it will work for a short while and then the sqeal will return! You need brake GREASE - I use a tube of synthetic stuff from NAPA - "SilGlide" or something like that - it works great.
Rotors rarely need to be turned except in strange circumstances. If they're warped, replace them - they're relatively cheap and last a LONG time. If they're not warped, don't shudder or shimmy, and are above min spec - just forget it and install new pads. I can't remember when I last turned a rotor, and I know it was never on a Mercedes...!
Regards,