Installing filters in the C is super easy. open hood take off engine cover, unscrew it, place in new filter, screw it up, put it back on. usually 15min job.

Stock filters are good enough when compared to K&Ns and the rest, it's been proven on the track and dyno for C63s. If anything just remove the charcoal filters because they shouldn't be there to begin with.

Running K&N's on mine. Fit perfectly, no issues and no MAF malfunctions.