It is not easy to re-install your server via SSH. You need to speak to your host company that will help you about this or it can be done out of your client area in case your provider enables you to do this.
Like others said, its not possible to re-install OS uing SSH but you can do some cleanup....but re-install should be faster than the cleanup and provide perfect output than working with SSH. Snapshot restoration can only help if you want to restore your VPS into certain level....otherwise go with the default OS reload.
If you want to reinstall the VPS, You need to have access of client panel which is provided by your hosting provider like SolusVM Control Panel. There you will be having option to reinstall the VPS with OS templates. You can choose your preferred OS template and go ahead with next process.
Reinstall is always good even if you have to do some work becuase that will get you latest OS with latest security fixes. In amazon, you can install OS in one main partition and can attach volumes to any new instance and can use. So it is good to have a new instance , Install the Softwares needed (only those which are needed and its latest) copy the configurations and fix the configurations , then attach the /home from old to new instance . In this case, time needed for copying the files and contents will be saved and you will be getting latest OS and other Latest softwares. Entire VPS snapshot will be having the same old server and old versions as far as I know