Nasty sounding drivetrain

Hi guys, I just finished a 50 km race yesterday (a new achievement for me!) and it was a total mudfest all the way because of the heavy rain in the area. So, the problem is, around a quarter way through, the really deep mud started (up to above the disk rotors). After riding through them, my drivetrain was making horrible grinding sounds in the bigger gears, especially on the uphills... My brakes were also grinding a lot but the sound would go away if I jist dragged the brakes fot a short while.

The question is, should I replace my chain cassette and brake pads or just clean them and hope for the best?

Regards,
Jimbo.