Principal Information Security Architect with 20+ years of cybersecurity domain experience in threat modeling and the design of architectures and information security controls. Ability to communicate with a broad audience from management to junior staff, both the technically aware and the technology-averse alike.
Moving the entire site (domain, site structure, etc.) intact to another hosting service will have not affect on your Google search rankings.
You need a SSL certificate. You can purchase these from many place or from your hosting service.
You need to install and configure the certificate on your web server.
I don't know what technical challenge you will face. I don't know your level of technical proficiency.
I have used CloudFlare for the last year to protect my web site from attacks.
CloudFlare’s technology automatically detects new attacks that arise against any website on its network.
Read more about CloudFlare's security features here: https://www.cloudflare.com/features-security