What does your petal look like?
Like this?
Pedal stiffness is dictated primarily by the pressure plate fingers. That is after all what you're pressing against to release the clutch. I suppose it's possible for the spring tension to weaken on these fingers and
pedal pressure to change. A fail[ing] csc will typically have a fluctuating grab point, or even all the way at the floor and dead
pedal for majority of its travel.
Changing clutch fluid is very easy. Just did it a few days ago on mine. You'll need some apparatus to remove the old fluid from the reservoir (but not completely), then either gravity bleed or have a helper pump the
pedal slowly then hold while you open and close the bleeder screw at the trans. I did a combination of gravity bleeding to flush new fluid through the system, then a helper for good measure.
Post a pic of your clutch fluid reservoir with the cover removed.