I will be happy to answer these questions
. Replacing the tubes is actually quite easy. The module with the tubes mounted inversely visible on the right is equipped with a hinge. If you need to replace the tubes in it, you need to raise the metal tongue, visible at the top right. Then the module can be tilted backwards and the vacuum tubes and horizontal deflection transformer become available. The tubes in the head are also easy to replace. The head can be moved to the rear by loosening the two screws.