i've been respraying the calipers on the front end and when i took them off i saw that the rubber seal around the piston was a bit worn and bits were coming off. seemed as good a time as any to put some new seals on it.

i know i'll have to bleed, probably flush the system, but aside from that how easy is this? i've got some brake lube for the pins and new rubbers and a piston pushing tool.
is it just a matter of pulling the piston out and chucking in new rubber?