You can run terminal commands, so I think we can manage this problem. Install mkusb-nox or the not yet officially released version dus. mkusb-nox tools can install a live system and dus can install a live or a persistent live system with Kubuntu in the external drive (both work in text mode, dus can work in graphics mode too), if that is what you want.
See the following links
dus - a revamped interface of mkusb and mkusb-nox
Or do you want to make a full installation of Kubuntu into the same drive as where you have the text mode system? It might be possible, but more tricky, because I suspect that that you have to edit the partition table in text mode. It might be better to do it in several steps:
Create a live drive (in the USB HDD or in USB pendrive or in a DVD disk),
Boot from that live drive and install Kubuntu into the internal drive.
You can check the S.M.A.R.T. status of the HDD. In graphics mode you can use Disks alias gnome-disks, and in text mode you can install smartmontools and use smartctl for this purpose. (See the manual to find out how to use it. Ask in a comment here, if you need help to select options.)
sudo apt-get install smartmontools