You can take the power from the ISO-Connector to the Radio.
If you are going to cut the wire to split it, don't forget to remove the
fuse
for the radio in the fusebox, you don't want to blow up the fuse and that
asking yourself why the radio isn't working anymor.
The radio also should have a wire for the Tel-Mute, usually it is written
on it with a label, otherwise check the manual of the radio.

And of course, don't forget to read the manual of the carkit and follow
the installation instructions.

Good luck and feel free to email me for instruction in Dutch, I also live
in the Netherlands (Rotterdam)