Seriously?
Double posting on something that, if, GOD FORBID, you actually browsed around at the other 4 million "HOW I REPLACE INGAME ITEM FOR ANOTHER?
?1?" You could get the answer to?
Honestly, 1 in 4 topics must be about this, it wouldn't have taken long.
Use:
http://mabimods.net/index.php?action=tpmod;dl=item33Find the item you want to replace.
Rename it.
Put it in the correct folder (HINT: IT IS THE SAME ONE YOU GOT IT FROM)
Run mabi (That usually takes a double click. Please refer to your manual for more assistance)
Mabinogi Status