upgrade to 2.5

I have upgraded joomla to 2.5, now the links in Finance are not working. If I upgrade the Finance Template will it overlay all of my work?

If you previously use Joomla 1.6 or higher you need to overwrite all template files via ftp connection which will surely have affect on your changes. If you previous version of Joomla was 1.5 you need to install new template because templates for Joomla 1.5 and 1.6+ are separate products and there is no option to update template from 1.5 ->> 2.5

Any advice in staging the upgrade so that I can keep my changes? Also will I need to upgrade News Show Pro 4?

I still don't know what is your current version, if 1.6+ the configuration of template, modules etc. should be not changed after upgrade process.