Since I didn't see a repost in the W210 section - let me try to be helpful.
The W210 E230 brake system has no tricky stuff - any competent wheel/brake store can do the work - EXCEPT you have to be clear that the lugs on your E320 MUST be hand tightened only !
Sensors: Only need to be replaced if a worn brake pad light has come on. They are all cheap - the OE Pex brand are like $1 internet aftermarket - autohausaz.com - any compatible sensor will do.
Brake Pads: In general with W210 front pads wear twice as fast as rears, so fronts go 1st, then rears get replaced about every 2nd front set. The OE pads are made by Pagid and are about $60 for front set, and Pagid rears are about $40. However, they are two types of rears - 1/pin and 2/pin so you need to look at the rears to see what type of rear pad you need to order.
Owner's sometimes look to see what type of other pad they can use to be either cheaper, or what other pad they can use to reduce the brake dust that gets the wheels dirty. There is no real - "best" - pad, most owner's that switch to other pads for either lower cost or lower dust in general are happy with their own choices for their own reasons.
In semi-metallic pads OE type, I personally don't like Mintex (owned by Pagid), but like Textar (owned by Pagid).
Personally I really like "Premium Posi Quiet" pads made by a large China supplier because they are made very well and have a rubber/vinyl coating on the back plate which aids in easy install and easy removal next time. These Posi Quiets are sold cheapest under Centirc brand like $35 for fronts and a little less for rears:
Rotors need to be replaced if they are too thin - Zimmerman Coat Z is what your MB dealer would use today - $140 front pair and $85 a rear pair from aftermarket like autohausaz.com. ATE or Balo is also OE quality. Well made no brand or quasi brand zinc plated rotors, also slotted/drilled - are also a affordable buy on the net.
The strategy would be to pull the parts you need from the net - then find a shop to do the install/labor - labor all 4 wheels rotrs/pads ballpark $125-$175 - again you do not need a MB specialist for this brake work.
BenzWorld.org forum is one of the largest Mercedes-Benz owner websites offering the most comprehensive collection of Mercedes-Benz information anywhere in the world. The site includes MB Forums, News, Galleries, Publications, Classifieds, Events and much more!