That's well within possibility, so long as you know where to look and have a plan to follow.
Just as a simple example, your status effect for your item can start with a simple piece of code like this:
Code:
<applicationCondition><![CDATA[[
#npc.getClothingInSlot(IS_PIERCING_EAR).getName()=="cattle tag"
]]></applicationCondition>
<!-- If the character is wearing the cattle tag, return "true" and afflict the Status Effect -->
<applyEffect interval="3600"><![CDATA[
[#npc.setHornType(HORN_TYPE_CURVED)]
]]></applyEffect>
<!-- Applies a transformative effect every 3600 seconds (one hour) to give the character curved demon horns, while the effect is active. -->
There are other basic functions like "setHornType" located and organized by body part within the game system's "GameCharacter.java" file, along with many other functions. The other half of this is figuring out how to find possible values of what to you want to use, so you'd look at things like "liliths-throne-public/src/com/lilithsthrone/game/character/body/valueEnums" to see possible values.
Innoxia (and whomever is helping them) has written up a bunch of example tutorial files that explain things in further detail.
It also helps to just glance at other modders' work to see examples in action.