I have seen a lot of traffic stating that the # 6 glow plug can only be changed by removing the injection pump. Not true. I belive that if it is there, it ought to work. Here is a technique that you can try:
You need a standard length combination 12mm wrench (5 3/4"),
and offset 8 mm wrench and an offset 6/7mm wrench.
The plug has a copper strip that needs to be loosened with the 8 mm offset. Once loosend, the plug can be removed.
To remove the plug, you will find plenty of room for a wrench behing\d the engine but no room for your hand. take the 12mm wrench and slide the 6mm offset through the box end. The 7mm side won't fit but will stop at the box end. Now you have a jointed tool that can be inserted into that space behind the engine making an easy job of removing the plug.
To replace the plug, take the copper strip and turn it around. The end for # 6 is split and for # 4 is closed. Place the end for # 4 on # 6 and secure it with the 8mm nut but leave enough gap so the plug can spin frely. This is now your insertion tool for the plug. Place it in the hole and use your jointed tool to tighten it down. You may need a little leverage extra against the plug with something like a screwdriver to gently hold it in place.
Total time: about 20 minutes.
Find a friend and try it on his!