Tom,
Shoot cgarr a message. He's installed these in cases that don't have them and he's replaced existing squirters as well.
I recall him saying that removal isn't terribly difficult. He did mention that staking the new ones in place is harder than you think. Porsche must have used some kind of rig to stake them because it's a very clean dent in the case material. Whereas doing it by hand takes some finesse and a good tool choice to avoid having it look "hacked"
He did this service for me on my 3.0L case when he installed the main web shuffle sleeves (his version of shuffle pins) in the through bolt holes. It's similar to what Neil Harvey shows in this thread
http://forums.pelicanparts.com/911-engine-rebuilding-forum/951269-home-built-engine-build-saving-unsaveable-2.html#post9772917