Yes there should be an isolator, but that might not be where you expect it. For example is it on an external box?
The installer will only have the standard length of ethernet supplied with the modem, typically only a metre or so length. It's not their fault if you don't have a power point near where you want the modem. Surely though there would be one nearby because of the computer
And as for the CD, no you shouldn't need one. Indeed it's always been possible to connect without one, unless you were trying to use USB.
The modem should have been active virtually staight away. If the sync and ready lights are on then chances are it is. You just need to follow the registration procedure using the details the installer left, or VM previously sent you. You may need to power off the modem and computer to get it to fully recognise each other's existence when you reboot.