Don Martin with Hunter Marine Customer Service provided me with the following information about our 1991 P42. Ive edited his response a bit for clarity:

The rudder bearings are sleeves that are made from UHMW material. The sleeves do not require any lubricate. There is no adjustment on these bearings. If they develop too much side-to-side play then the bearings would need to be replaced. Anything over 1/8th inch play would be considered outside of tolerance and the bearing would need to be replaced.

In another e-mail to Don I asked him whether it was a matter of dropping the rudder and popping the old bearing out or did it require special tools? He said that after the rudder is removed you should be able to remove the bearings by driving the top bearing out and from the underside of the boat you should be able to insert something like a 1 x 2 up into the rudder tube and there should be a ridge at the bottom of the top bearing, you should be able to get the 1 x 2 on this ridge and drive the bearing up. This would be reverse for the bottom bearing.