If it takes 16+ hours of labor to disassemble a trans, the person doing it must be using their feet instead of hands. I know a 700r4 is an older transmission, but I can get one out of a car and apart pretty damn quick.
So let's get something straight, He has an 04 Seville STS(FWD). As the Cadillac STS(RWD) didn't exist until the 05 model year.
The FWD transimission rebuilt is less than $2000.
http://www.automotix.net/transmissions/2004-cadillac-seville_sts-automatic_transmissions-4t80e.html
I can find 25K mile used transmissions out of 05-08 STS's for less than a $1,000.
Rebuilt units go for around $2000.
And if they were so horrible in the 05 and up's why is the 5L40E used in the STS, also used in BMW's?