Thats a really good deal unless there is something wrong with the car. Get it checked out by a mechanic. Those cars really hold their value well and in good shape I would think its worth a lot more than $2,900 and with such low mileage.
If you have seen the car in person and know that the guy actually has the title for it, then have it checked out by a mechanic and grab for it ASAP. [Just verify that WX3 is on the SPID label to know that it is a real SS.]
If this is internet listing and you have not seen the car in person, BEWARE! There seem to be a lot of scams recently involving very low-priced '96 SS's. Do not send/give anyone that you do not know money for a car until you can put your hands on the car.
Did you see it on craigslist? There seems to be a scam going around right now with an SS listed for that price in many, many different cities. The car is supposedly located in Florida, regardless of where they say it is in the ad.