I would be a $50 part if it were installed in a ford but because the you need a plug that only fits a MBZ you are stuck! Unless, you buy one for another car with the same size mounting hole in the exhaust pipe and cut and solder in your old plug-ins. But $170 seems high... check on-line and see if your mechanic will come close. P.S. DON'T comprimise on quality here.
The tower is a different story. My mechanic just drilled mine out and left in open so he could always have access to it. Legally, Federal emmissions laws, it is ONLY supposed to be adjusted by the mechanic. So you really are stuck.