My tips are:
1. Don't do this via Normal.dotm. That template might have been customised by the individual user and you would be over-writing their personal productivity tools. Instead, consider doing this via an addin (template loaded as addin) or as a template which can be attached to existing documents or used to create new documents.
2. Custom UI Editor is a free way to edit the xml but you need to learn the basics of the RibbonUI xml. Years ago I knew of a relatively cheap xml editor that puts a GUI in the way so you didn't need to learn the xml. I can't recall its name but your GoogleFu might reveal it.
3. Software developers might choose to use Microsoft's Visual Studio or VSTO to create Office solutions which include buttons on ribbons. If you are worried about learning xml then this is not a good option for you but you could hire a developer who knows their way around in the tools.

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Andrew Lockton
Chrysalis Design, Melbourne Australia