Why upgrade if they still like the desk? I guess the computer itself is behind the closet door on the right, and ventilation probably isn't great in there. And the niche for the monitor might be a bit too small for a 27" or even a 24" screen, but removing the top shelves and adding a couple of vent screens for ventilation would solve those issues.
No, people bought them for cheap in the '80s because they must have been mass produced because I'm pretty sure everyone had one including our family, and still had them in the '90s.
Wow, that looks almost exactly like my desk design wise. Only difference is the design of the 2 drawers hinge and the leg area has an overhang to put your feet up.