Uninstall or delete modules when upgrading 6 to 7? Sorry to ask such a basic question, but I can't find an answer (and I'm an amateur).

I have a website that was written for me in Drupal 6. I want to upgrade it to Drupal 7.

There are quite a few contributed modules, and I realise I need to disable these before upgrading the core. Can I then simply delete the unused modules via FTP, or do I have to use uninstall within Drupal?
Updated after re-reading your question. :)

The process for completely removing a module is generally:


Backup your site.  The Backup and Migrate module is great
here too. 
Disable the module. Admin -> Modules -> Uncheck module ->
save. 
Uninstall the module - Goto yoursite.tld/admin/modules/uninstall ->
Check Modules to uninstall -> Click Uninstall
Delete the module - Delete module directory.




Additionally you can find details regarding upgrading from previous versions of Drupal at drupal.org.

Another useful module is the Upgrade Status module.  Listed only for reference.