ETA when engaged locks the fork out at a reduced travel. not a lock out per say as it still gives you some bounce great for climbing hills as it drops the front end enough so as not to wheelie.
to test if it is working or not, engage the ETA by turning the adjuster (to the rear if i remember correctly) on the left leg, put as much weight as you can on the forks if they stay down it's working if they just pop straight back up to full travel it's not.
as for servicing the seals/bushes i payed my LBS to do it for me (didn't have a 21mm socket at the time to get the internals out), but honestly i don't think it would be that difficult.