I would like to uninstall the current version 4.2.9 and then reinstall version 4.3.0. At the current time it will not create a sitemap, giving me the following error (Your sitemap file is deprecated or not created. After you make all the changes, you should hit the Generate XML button.). Even following the instructions does not work.

My concern in uninstalling the current version is that I will lose my current JoomSEF urls. Will that happen?

Hi,

If you uninstall JoomSEF, the "_bak" string will be appended to all its database tables names. So your URLs will stay in database, but they won't be accessible right away after new installation.
But after a new installation you can replace new JoomSEF's database tables (the ones starting with _sef) with the ones containing the "_bak" suffix.

Of course you should back up your website before making such changes (or before updating components in general).

Maybe a bigger problem is that you will also lose your JoomSEF configuration.

Anyway I don't think that uninstallation and new installation will make any difference from standard update, so I think you can just update your JoomSEF without losing anything and if that doesn't help, we can try to work out what's wrong with your Sitemap generation.