Remove the through bolts in the U-joint, take a self tapping screw and start it in the groove that the through bolts sqeeze together, let it soak with somekind of penetrant, take a long punch and drive it up the shaft and then pull it back off of that shaft once it is free of the rack. I have occassionally had ones that it was necessary to put a small slide hammer on to pull back down the shaft but I am in the business and it had to be done NOW, I have no doubt that if you let it set with some good penetrant like kroil or pb blaster it will probably slide right off in your hand, especially if you put the screws to it to spread it open a little bit. I imagine most, not all of the U-joints are interchangeable on the 240's and seeing as how I have had very very little call to replace them (I'm in So. Cal, home of killer weather) I would think that you could get by with a bone yard replacement. If by the "whole assembly" you mean the column complete I would have to say no. Replacing a column for a bad U-joint is overkill, but if you mean just the joint itself well then yes that is entirely acceptable.

Mark