As I recall the six speed manual is $1500 from GMPartsDirect. Unless you are a mechanic and have access to a lift, I would expect labor to be around $1000 including changing the shifter, the cost of which I have not seen but expect would be about $300.
An upgrade like this does not normally increase the value of the car, and would very likely subtract from its value. Of course one could etract these parts from a wreck and save some bucks potentially giving up on reliability, but new, rebuilt, or just plain used, that is a lot of money for a potential 2 miles per gallon mpg improvement.
Laborsmith