The fuel filter on a '91 Probe GL, which may or may not be the same, but I believe it is, is located near the firewall on the drivers side near the master cylinder and break fluid reservoir. It fits into a bracket type clamp in a vertical position. Should be fairly easy to replace.
-Shaun
The Fuel filter for a 94 Ford probe GT is located under the air filter assembly next to the driver side front wheel well
Inside the transmission.
Inside the trans pan
If it is a 4 cylinder it is on the back of the motor by the firewall.
Filter is mounted on the left side engine/transmission mount. Under the cruise control actuator.
In the trunk to the far left side under the floor board.
The thermostat is located on the right side of the engine looking in, in between the intake manifold and the air filter box, underneath the wiring. This is in a 1994 Ford Probe GT 6 cylinder
On the bottom of the tranny catch pan. You will have to remove the gasket seal with 12 screws then the filter is right there.
The fuel filter is mounted on a bracket affixed to the rear of the left-hand side motor/transaxle mount.
Facing your engine, it is on the right side underneath the air intake filter assembly.
under the hood on the firewall It's right about under the brake resevoir, black cylinderical.
drivers side enigine compartment by the strut tower between the air intake hose and firewall