it can be done but it's one of those 'you might aswell do it' things. Do it right the first time around. the FSM does specify greasing the mating face when replacing axles.
if you dont want to take the axles out, you can remove the big nut and push the axle out as far as it will go then use a brush or similar tool to apply the grease. it's very fiddly due to space constraints and u cannot clean out the existing crud and corrosion unless you remove the axles.
set aside an afternoon and that should be enough time
