For MetaMod 1.5 (for Joomla 1.5), no core changes are necessary. It's a very normal module installation, and the module can be upgraded or de-installed completely normally.
For MetaMod 1.0 (for Joomla 1.0), there is a core change that you can make which helps MetaMod to display a list of other modules right there in MetaMod. This helps you to get the module ID numbers. Read about it here.