Rear-facing third row seat

Has anyone one here ever installed an aftermarket third row seat in a Taurus station wagon?

I've got a '99 wagon, and I've seen kits complete with belts for $300 to $400.

I'm wondering mostly if they are safe - obviously the seats are for my kids and safety is #1 for them. I can't seem to find any info on the www concerning the safety of these things.

Secondly, I'm curious about the difficultly. I'm a scientist, NOT a mechanic. I do my own oil changes, brake pads, minor repairs, etc., but major items/issues I take to the shop.

I've got almost 160K on this thing, she's treated quite well, and I really would like to keep her until the kids are too big to fit in it! (With four of them - they don't fit right now! - unless I add the extra seat...)

"When a minivan with a third-row occupant is hit from behind, the occupant is killed half the time, according to a Ford Motor analysis." I took that off of this page;
http://www.usatoday.com/money/covers/2002-03-01-car-seat-safety.htm

I have 3rd seats in both of my Taurus wagons, only time my 2 boys were allowed in them was when the car was sitting in the driveway..