My car is picking up on the mileage and age. Was wondering if there is any benefit, performance gains, by adding a new fuel filter? I'm looking to mess around the car today, was down at the parts store looking for something I could do with the car? Clerk suggest fuel filter? I'm on line trying to find something that shows how much work this would be also! :)

I don't believe you will gain any performance by changing the filter.I have read the older C5's with high mileage had problems with the filter leaking.So It would benefit you to change it.
I would get the Fram brand of fuel filter.The 97-98 filter is the one you need.The design changed on the 99-04.
1. Disconnect the battery.
2. Relieve fuel line pressure. On the drivers side fuel rail under the FRC is a schrader valve.Take a small screwdriver and a rag and depress the the valve.Hold the rag over the area to prevent fuel from spraying.
3.Raise vehicle,the fuel filter is located on the left rear frame rail.The filter has plastic clips holding it on the line.Depress clips and remove filter.When replacing it with a new filter use a little oil on the inside of the clips of the new filter for easier installation.
4. Check for leaks when finished.

5. The 99-04 filter change requires a fuel line disconnect tool to remove filter.The 97-98 does not.

Good luck and becareful

No gains, you will simily be getting the fuel the engine needs with less work by the engine.

I don't believe you will gain any performance by changing the filter.I have read the older C5's with high mileage had problems with the filter leaking.So It would benefit you to change it.
I would get the Fram brand of fuel filter.The 97-98 filter is the one you need.The design changed on the 99-04.
1. Disconnect the battery.
2. Relieve fuel line pressure. On the drivers side fuel rail under the FRC is a schrader valve.Take a small screwdriver and a rag and depress the the valve.Hold the rag over the area to prevent fuel from spraying.
3.Raise vehicle,the fuel filter is located on the left rear frame rail.The filter has plastic clips holding it on the line.Depress clips and remove filter.When replacing it with a new filter use a little oil on the inside of the clips of the new filter for easier installation.
4. Check for leaks when finished.

5. The 99-04 filter change requires a fuel line disconnect tool to remove filter.The 97-98 does not.

Good luck and becareful

I appreciate your help, I ended up spending my time at shop and had them give the car a good tune up. Actually I'm now thinking about adding some new life to the car! thanks again