Oceanis 311 tiller leak

The tiller stock on my 311 has a small leak from the deck through the upper bearing, with water accumulating in the bilge. I have read that a common cure for this is to put some grease around the top of the bearing. But I have also read Beneteau advice that no grease must be used on these bearings, only WD40. So, is there is a simple fix? Do I need to replace the bearing and, if so, how difficult is this?