X-no-Archive:yes
I'll put my foot in this one...

It's not the presence of graphics that makes the interface intuitive or
'user-friendly'. One can certainly write a character-based system that has
equivalents to the check boxes, radio buttons, drop down lists and a menu at
the top that we associate with a GUI. The main advantage of 'going GUI' at
this point is that it is much easier to find and buy for cheap the GUI
development tools that make building the screen child's play, but there are
very few of these for character-based systems, and fewer for the 3000. But I
know that I have worked with bad GUIs. And the existing app will have to be
in some measure reworked to become more intuitive; bolting on a GUI will not
do this for you.

So it seems to me that there are three ways to approach what is two distinct
tasks, reworking the app and creating a GUI, that can be done in either
order. If you create the GUI first, it will have to be reworked with the
app. Or these can both be done at the same time, which makes for its own
challenges and pitfalls. At this point, it becomes a question of other
constraints, of what you are being told to do and what you can deliver, or
what projects you can sell to whoever makes these decisions.