The need is to reinstall panels because of some issues with it. However what will happen to the already existing panels if you reinstall or even remove panels entirely?
You will lost your custom panel configuration. To prevent that you can export all your panels to code with features.
This is because modules should remove its own data on hook_uninstall.
Features provides a UI and API for taking different site building components from modules with exportables and bundling them together in a single feature module. A feature module is like any other Drupal module except that it declares its components (e.g. views, contexts, CCK fields, etc.) in its .info file so that it can be checked, updated, or reverted programmatically.
This way you will have a features module with all your panels configuration.
This are the steps:
- Install features module.
- Go to admin/structure/features/create
- Give a name to the feature module.
- Select panels configuration
- Download the feature.
- Move this module to the features folder (site/all/modules/features).
- Uninstall panels
- Enable panels
- Active the feature on admin/structure/features
There are also 'export' and 'import' tabs/links on the Panels UI and Pages UI but this is a manual process and can be slower than using features.
If all you are doing is replacing the code and not disabling and uninstalling the module, this won't affect your existing panels, however it is always a good idea to back them up using either the method mentioned by jorgetutor or a full database backup (always useful)