I tweaked MOSG to change the lighting (it was a bit too dark for me), thought I'd done that and only that (seemed quite simple). Yet when I re-loaded up my game everything seemed fine except my landing-from-a-jump sounds have changed to some diferent, annoyign sound. Can anyone suggest how I can get the jump sound back without having to reinstall stuff etc etc? Please bear in mind, I am an idiot. Thanks!

Go through the Sound folder in the data files, go into fx, then into FOOT, and find the sound being used, and possibly another sound you may want instead in the folder or subfolders (If any) and replace it. Vanilly game should simply by Land.
Path (Windows 7/vista) C:\Program Files (x86)\Bethesda Softworks\Morrowind\Data Files\Sound\Fx\FOOT

Thanks man