1. Upgrade Magento to latest stable version (currently ver 126.96.36.199) from ver. 188.8.131.52
2. Update extensions if required to work with 1.5:
3. Allow for importing and updating of simple and grouped products via Magento import tool.
If we need to install an additional extension to get the grouped product import to work that is ok, such as:
[url removed, login to view]+-export-with-tier-pricing--product-custom-options--configurable-products--bundle-products--grouped-products--downloadable
4. Ensure theme compatibility with Magento 1.5, especially custom theme templates