Has anyone here done that?
Yes. I run both Bitcoin Core and BitcoinABC on the same computer (Windows 10 Pro x64)... As an aside, I have also run Bitcoin Gold on this machine.
What should we be looking out for or should take note of specifically to make sure it all goes smoothly? All tips are appreciated. From some research, I know the datadir's and the port's used to map to the same place, but I don't know if this is still the case,
and what about the files installed themselves, do they map to the same directories and how should we re-work the code? ie. Can we run both daemons at the same time?
Be VERY CAREFUL when you install BitcoinABC. As you already know, it WILL attempt to hijack the datadir... and YES it WILL attempt to install itself over Bitcoin Core
That is to say, BitcoinABC will attempt, by default, to install to C:\Program Files\Bitcoin
and it will attempt, by default, to use the datadir C:\Users\YOURUSER\AppData\Roaming\Bitcoin
You CAN make it use it's own locations... you just need to be very careful when installing to specify a different install directory and when running the clients to ensure that you use the appropriate -datadir arguments when launching the apps (I modified the shortcut for Bitcoin ABC).
I can run both GUIs at the same time without issue. I don't use "-listen=1", so because I don't have incoming connections, I don't think having the same "port" is a problem. If you needed to use "listen=1" to accept incoming connections, I could see this being a potential issue.