What's the procedure with changing domain settings? We just change the IPS-KEY to yours, assuming 301 redirects are in place?
No, first the DNS servers will need changing to:
This is best done before the TAG is switched in case the existing DNS records are removed at the point when the TAG is switched. Or we can do it afterwards, but if it's done afterwards there is a danger that there will be a period when people can't access the site.