Whether or not they're a "deal" is in the eye of the beholder. You're the one spending the money, after all.

As I understand it the series III (your first link) is about the same install as its predecessors, though you either have to convert back to a cable-operated throttle body or go where most haven't and convert the Fiero's throttle to drive-by-wire.
No idea what's involved with a 3.9 install.