Not sure, but I believe most GS' were 4 cyl Zetec.
Check used car prices online for average price. Without knowing what options are on the car, hard to tell, but $9k seems a little high.
"My Name is Richard. I am a Contouraholic." 1999 SE Sport Duratec ATX Spruce Green; Drop--In K&N Filter; VentShades; Fog Lamp Fix Mod & PIAA510s with Bumper Braces & Stock Type aiming screw mod; PIAA 9006 Super White Headlamps AIWA CDC-MP3 HU; WeatherTech Mats Viper 600ESP w/Remote entry