How to create custom WPF ribbon tab for COM AddIn

Question

Hello, I have a shared COM AddIn (not VSTO) for excel 2003, now I want to add a ribbon tab to support excel 2007. I did some research online. know that I need reference 2007 PIA, implement IDTExtensibility2, IRibbonExtensibility in my connection and IRibbonExtensibility has only one method string GetCustomUI()

    string IRibbonExtensibility.GetCustomUI(string RibbonID)
    {
        return Properties.Resources.Ribbons;
    }

I add ribbons.xml in resources, ribbons.xml is as follows:

Not sure if this is the good/right way to do. I want to customize like add icon to button, largeimage, smallimgae, connect command to button, etc. I feel in xml, it is hard to do this.

There must be better way to achieve this, please let me know how

thanks