Why are you replacing the wheel bearings? They aren't consumable items as are the seals. Wheel bearings are replaced only on an as-needed basis.

They do need to be cleaned and repacked every time they are opened, or every 90K.

If you insist on replacing them, it can be a DIY. The toughest part is removing the old outer races and putting new ones in without damaging them. The trickiest part is properly setting the preload. This topic has been written up many times. Please search the archives using the words "preload" and "wheel bearing".

__________________
95 E320 Cabriolet, 169K