SSL Cert (CSR) / Reinstall Plesk

[Ares]

Hey,
I want to reinstall my server, but I'm not sure if I can use my previous ssl certificates without my old CSR on the server. I think I won't need it because the certificate was already issued, but just to make sure...

And is it possible to use my old Plesk activation key again or do I have to mind something else?

Regards,
Ares