Switching ISP (PPPOE to DHCP) - Best Practice?

[sarkyscouser]

I'm switching ISP in less than 2 weeks and trying to plan out the best way to update my config to update the connection type, interfaces, gateways, default routes etc etc.

My current ISP (BT) is PPPOE/DHCPv6 and my new ISP (BRSK) is DHCPv4/SLAAC.

Can I achieve this via the GUI or do I need to go to the shell and re-assign interfaces? Which is the best way?

My current ISP uses PPPOE with credentials for IPv4 and DHCPv6 over PPPOE for IPv6 and they give out a /56.

My new ISP has no credentials, I need to clone the MAC address of their supplied router onto my WAN interface and then change to DHCPv4 and SLAAC on WAN to get a /48.

I've seen some posts about residual gateways and routes causing problems so how to go about this please?

I use Kea DHCPv4, Router Advertisements for IPv6 (no DHCPv6 on LAN) and Unbound for DNS if they matter.