I have spotted my filter, against the firewall and a bit below my master cylinder.

I am a full grown adult with normal size hands.

Just how the heck does one go about replacing that thing?

Also, any helpfull remarks about relieving fuel line pressure would also be usefull.

thx in advance and I will respond back with how the work went.

 

I have a '93 wagon. Still not easily accessible, but this procedure makes it a little bit easier.

To remove fuel filter:
Disconnect battery and remove from vehicle.
This gains you access to band screw clamp that holds fuel filter against firewall.
The plastic "U" clips on fuel lines need to be slid out perpendicular to hose/line.
Replace clips with new ones if not provided with fuel filter.
(If confused on how to remove U clips, I suggest you go to parts house to examine how the fuel line clips and connectors work)
Installation in reverse.

 

There is a schrader valve on the fuel rail under a black cap (looks like an oversized tire cap with a 1/4" flat tab on it).

Procedure:
Wear protective gear as needed (glasses/apron etc.)
Engine off.
Remove the black cap on fuel rail by unscrewing CCW.
Depress schrader valve gently
Be careful as the schrader valve may leak after you relieve pressure.
Be sure schrader valve spring returns up to seal. If it does not gently (and I do mean gently) pull up schrader valve pin to return to normal static position.
Once pressure is relieved you are able to work on fuel system.
Upon reassembly verify that the schrader value is holding pressure and does not leak.
If schrader valve leaks replace with new from dealer or other reputable source.
(An air schrader valve, such as on a tire, IS NOT the same as it is not rated for use with fuel/chemicals).

 

There is a possible alternative method to relieve the pressure in the fuel system before removing the fuel filter.
If you locate the fuse for the fuel pump in the fuse panel, just remove it while the engine is running and the engine will quit due to the lack of fuel. Try to start the car one or two times and that will lower the fuel line pressure to the point where you can remove the filter without a fuel bath. When finished replacing the filter , reinstall the fuse, turn the key on then off a couple of times before starting the car. This will give the pump time to build up pressure in the lines and allow you to check for any leaks before starting the car.