SSL and webaddress

[dave.81]

We have been running V7 of HAP for awhile and students/staff link via an IP address (000.000.000.000/hap) and get an SSL warning, this has been fine up until now but our Headmaster wants to change this to linking to a subdomain ie; remote.school.co.uk and remove the SSL warning. I'm planning on upgrading to the latest version and sorting these issue for him but am unsure.

 

I've never got involved with DNS/web forwarding etc as we have not hosted our own website before.

 

We have a domain that we've purchased for some other upcoming projects so can i use that domain to some how redirect to the IP of the internal server?

I can buy a basic SSL from 123-reg for £10 would this then work if i installed it onto the server running HAP?

 

I know i should know this but having never got involved with this before dont want to give answers that are wrong.

 

Thanks!!!