You would do well to search this TDr forum for advice and pictures. I converted my fronts from standard VW to Discs with wire wheels about a year ago. Happy Jack converted from drums to discs (both with VW wheels) a few months ago.
The wire wheels may cause a problem, I had to do some modification in order to get mine on. My wheels are 14″ from a Triumph Stag. The setback or offset on wires may be different enough from VW and cause direct contact with the disc calipers. Depending on which disc kit you buy, your track may increase a bit. Mine came from SoCal and increased track about 3/4-1″ – hardly noticeable.
Happy Jack’s swap was painless and only took about 2-3 hours total including bleeding and my kibitzing.
Sorry, can’t help with the rears but on mine, the front discs made such a difference you may not want/need to do the rear.