Ok, so what I want to do is when you pick up a "coin" the game will display the same overlay as when you get an achievement but with a custom item along with custom text. Got any ideas?

I have tried doing that but, I am stilling learning about OpenGL and such with Java. Here's something I wrote up but I'm not sure how to put it on screen when picking up an item:

 

@SideOnly(Side.CLIENT)
public class GuiCoinCollected extends Gui
{
    private static final ResourceLocation texAchi = new ResourceLocation("textures/gui/achievement/achievement_background.png");

    /** Holds the instance of the game (Minecraft) */
    private Minecraft theGame;

    /** Holds the latest width scaled to fit the game window. */
    private int width;

    /** Holds the latest height scaled to fit the game window. */
    private int height;
    private String headerText;
    private String coinNameText;

    private long unlockedTime;

    public GuiCoinCollected(Minecraft par1Minecraft)
    {
        this.theGame = par1Minecraft;
        this.headerText = "\u00A7e" + StatCollector.translateToLocal("crewMod.coinCollected");
        coinNameText = "";
    }

    /**
     * Update the display of the achievement window to match the game window.
     */
    private void updateWindowScale()
    {
        GL11.glViewport(0, 0, this.theGame.displayWidth, this.theGame.displayHeight);
        GL11.glMatrixMode(GL11.GL_PROJECTION);
        GL11.glLoadIdentity();
        GL11.glMatrixMode(GL11.GL_MODELVIEW);
        GL11.glLoadIdentity();
        this.width = this.theGame.displayWidth;
        this.height = this.theGame.displayHeight;
        ScaledResolution scaledresolution = new ScaledResolution(this.theGame, this.theGame.displayWidth, this.theGame.displayHeight);
        this.width = scaledresolution.getScaledWidth();
        this.height = scaledresolution.getScaledHeight();
        GL11.glClear(GL11.GL_DEPTH_BUFFER_BIT);
        GL11.glMatrixMode(GL11.GL_PROJECTION);
        GL11.glLoadIdentity();
        GL11.glOrtho(0.0D, (double)this.width, (double)this.height, 0.0D, 1000.0D, 3000.0D);
        GL11.glMatrixMode(GL11.GL_MODELVIEW);
        GL11.glLoadIdentity();
        GL11.glTranslatef(0.0F, 0.0F, -2000.0F);
    }

    /**
     * Updates the small achievement tooltip window, showing a queued achievement if is needed.
     */
    public void updateGui()
    {
        GL11.glPushMatrix();
        if (this.unlockedTime != 0L)
        {
            double d0 = (double)(Minecraft.getSystemTime() - this.unlockedTime) / 3000.0D;

            if ((d0 < 0.0D || d0 > 1.0D) || coinNameText.equalsIgnoreCase(""))
            {
                this.unlockedTime = 0L;
            }
            else
            {
                this.updateWindowScale();
                GL11.glDisable(GL11.GL_DEPTH_TEST);
                GL11.glDepthMask(false);
                double d1 = d0 * 2.0D;

                if (d1 > 1.0D)
                {
                    d1 = 2.0D - d1;
                }

                d1 *= 4.0D;
                d1 = 1.0D - d1;

                if (d1 < 0.0D)
                {
                    d1 = 0.0D;
                }

                d1 *= d1;
                d1 *= d1;
                int i = this.width - 160;
                int j = 0 - (int)(d1 * 36.0D);
                GL11.glColor4f(1.0F, 1.0F, 1.0F, 1.0F);
                GL11.glEnable(GL11.GL_TEXTURE_2D);
                this.theGame.getTextureManager().bindTexture(texAchi);
                GL11.glDisable(GL11.GL_LIGHTING);
                this.drawTexturedModalRect(i, j, 96, 202, 160, 32);

                this.theGame.fontRenderer.drawString(this.headerText, i + 30, j + 7, -256);
                this.theGame.fontRenderer.drawString(this.coinNameText, i + 30, j + 18, -1);

                RenderHelper.enableGUIStandardItemLighting();
                GL11.glDisable(GL11.GL_LIGHTING);
                GL11.glEnable(GL12.GL_RESCALE_NORMAL);
                GL11.glEnable(GL11.GL_COLOR_MATERIAL);
                GL11.glEnable(GL11.GL_LIGHTING);

                GL11.glTranslatef((float)i + 16, (float)j + 16, 50F);

                GL11.glEnable(GL11.GL_DEPTH_TEST);
                GL11.glDepthMask(true);

                GL11.glScalef(1.0F, -1.0F, 1.0F);
                GL11.glScalef(20.0F, 20.0F, 20.0F);
                GL11.glRotatef(10.0F, 1.0F, 0.0F, 0.0F);
                GL11.glRotatef(-22.5F, 0.0F, 1.0F, 0.0F);
                GL11.glRotatef((float)(Minecraft.getSystemTime() - this.unlockedTime) / 6F, 0.0F, 1.0F, 0.0F);
                
    			System.out.println("Gui Class: Ran");

                GL11.glDepthMask(true);
                GL11.glEnable(GL11.GL_DEPTH_TEST);

                GL11.glDisable(GL11.GL_LIGHTING);

            }
        }
        
        GL11.glPopMatrix();
    }
}

You mean a TickEvent?

Oh. I was still looking on how I would use that (no previous experience). I said I just wrote that class up as a base for displaying the achievement thing.

Where would I put that?

Oh I understand how to do it! But where would the ElementType.All need to be put?

Ok, let me go try that out.