If you suspect the bearings are bad it may be a good idea to repack the bearings. It'll give you a good opportunity to inspect the races. The noise may be something else rubbing. A bad wheel bearing noticeable when turning by hand would definitely be noticeable while driving. If you'll repack the bearings, you must replace the seal. The seal cannot be removed without destroying it -- believe me, I've tried!
The manual requires setting axial bearing clearance between 0.01 to 0.02 mm and requires using a dial gauge. You might get by setting the bearing clearance without the gauge, but these are rather tight tolerances and you'll be lucky to set them properly by hand. I'm fortunate to have a dial gauge available to me.
95 E320 Cabriolet, 131K