You can just do the OTA update without uninstalling. Or you can uninstall first then update. Doesn't matter, either way you will then be running the stock PR1.3 kernel and will need to reinstall the power kernel to overclock. However...You will not be able to just simply reinstall the power kernel. It will fail due to some leftovers not erased by the PR1.3 update. To reinstall, you must first uninstall the power kernel packages. Do not try to uninstall from the app manager - it will fail. You can uninstall by either clicking the uninstall icon in the app tray (slightly risky) or by following the manual deinstallation instructions found here (safe): http://wiki.maemo.org/Kernel_Power#Deinstallation