[1.6.4]Replacing Vanilla achievement requirements

Hi, I'm Java but have some knowledge of programming.

I've been trying to figure out a way to fix achievements in a mod that replaces vanilla's tool system but can't seem to figure out how to go about it.

I attempted to change the ID and put one in it's place but it is marked as final, so I attempted to override it and then i'm unable to call my method as it became non-static

main.java:

@EventHandler
public void load(FMLInitializationEvent event)
{
Achievements.registerAchievement();
}

achievements.java:

public class Achievements extends Achievement {

public Achievements(int par1, String par2Str, int par3, int par4,
		Item par5Item, Achievement par6Achievement) {
	super(par1, par2Str, par3, par4, par5Item, par6Achievement);
}

private static AchievementList achievementlist;

@Override
public Achievement registerAchievement() {
		achievementlist.buildHoe.statId = 0;
		Achievement mybuildHoe = (new Achievement(6, "buildHoe", 2, -3, Item.hoeIron, AchievementList.buildWorkBench)).registerAchievement();
		return mybuildHoe;
}

}

Any help would by greatly appreciated