I doubt there is an easy fix for this. You might be able to get a rebuild kit, but most people opt for replacing the rack since the rebuild IIRC is kind of difficult and pretty touchy. The seal that is leaking is internal, it isn't just that rubber boot.

You might pull the boots off and see if you have any leaking elsewhere too.

As far as the PS fluid, I don't recall if there is a big problem with flushing and replacing the fluid with PS fluid, but these 4runners definitely take tranny fluid, which is red, or more rust colored when it's really old. If you replace the rack, switch back to tranny fluid (the new rack will probably be preloaded with some tranny fluid, so don't just dump in PS fluid to a new rack) and flush the pump really well. I would pull the lines and let the pump pump through some soapy water or something like that, just don't let it run dry.

Is it just me, or does it seem like everyone's steering rack are failing all of a sudden?