in either case, i can help you,
if you wanna use your own ssl certificate (usually issued by a CA) then you must also have at least 1 dedicated IP address,that usually comes with VPS or Dedi-servers,
But Also you can use Cloudflare pre-built SSL (domain verification by Comodo) that comes free if you use their basic plan for your domain DNS settings.
the latter option is so much easier, since you do not have to pay for any SSL certificate to be issued or buy any dedi-IP addresses,
*PS:please make sure cloudflare allows your domain name to use their services( they block some domains violating their TOS).
it will be often really fast, probably one single day. in some rare cases, it can take some more time to optimize all website elements with SSL.
Yes!. if not ,your website would be suffering from "mixed content error" which I will try solve!
A lot of advantages : 1_ Better SEO . 2_encrypted communication between the visitors and your server. 3_better user experience.