Nothing very mysterious. If the sphere is still secured to the standing base, you start by opening the base from below and releasing that swivel connection, so the upper spherical part comes free.
The two halves of the sphere are secured with a few screws around that joint.
There are also a few chassis screws in recessed holes that you need to loosen from the back of the case.
Once inside, I remember a few more screws, but it has been several years. Of course, you need to disconnect the antenna terminals and speaker connections, pull off the knobs, etc.
Kind of a fun TV, if you don't mind working on a spherical chassis. (Hint: keep some bubble wrap on the workbench which you can fold into a soft roundy cushion while working on the chassis.)
The tuner is a notorious weak spot. I had one of mine repaired by a former JVC factory tech who griped about them. He said the typical VideoSphere service call consisted of pulling out the old unrepairable tuner, pitching it in a bin, and installing a new one.
If your friend gets stuck, send me an email. I don't want to pull my working one apart, but I have a second one somewhere in the shop, with halves already separated.
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html