Partial answer: you can have two buffers with the same content but different buffer-specific settings, such as different cursor positions (that aren't forgotten if the buffer isn't displayed in a window), different major modes, etc. This is called indirect buffers. Press C-x 4 c to create an indirect buffer for the current buffer and show it in a window. You can have one of them render the Postscript and the other show the source: C-c C-c only applies to the current buffer.
There are limitations of indirect buffers. For example, they both use the same font-lock settings. As a consequence, C-c C-c in one buffer removes syntax coloring from the other buffer, though you can get it back by turning font-lock mode on and off in the buffer showing the source.
To automatically update the preview buffer, you could set up an idle timer or an after change function in the source buffer that re-renders the preview.
There is no automatic synchronization between the position in the two buffers. When you're viewing a PDF file rendered from a source (e.g. LaTeX), there are ways to embed backreferences so that when you click in the PDF, the editor jumps to the corresponding place in the source. However, I don't know if that's possible with Postscript, and even if it is, it would require the Postscript source to contain those backreferences, which is probably not feasible if you're editing the Postscript manually.
