I press them out to keep them nice and square and likewise to refit as they need to be tight in the case - that's all that keeps them there, though I've never tried tapping them out as big john has suggested.
I also well support the case around them when pressing them as that first 'crack' can take a bit of force, most of these have been there a long while! I fit a deep socket over the Pin and land it in the base of the Pin to press them.
As big john also mentioned, the O Rings aren't supplied in the kits but are available as a separate part.
I fit them back with some Loctite, not just to help hold them but also to help with the sealing of them.