Your in luck, I have recently fitted a towbar to my wagon, if your towbar looks like the one in the attachment then heres how to do it.
You have to remove the rear drivers side, fuel tank strap bolt, making sure you remove the spacer. This is becase the towbar mounts on this bolt location and you will not need the spacer anymore as the plate will substitute this now. then you have to centrepunch all 5 holes (2 drivers side, 3 passenger) so you can see where to drill on the inside for the bolts (The holes need to be a large as the diameter of the spacers). Once all 5 holes are drilled, lift the towbar up with a mate and from the inside feed the bolt through the mounting plate and make sure you use the spacer which goes in-between the mounting plate and the chassis rail and do the nut up from underneath.
I had a Vn Wagon a few years ago and going by the picture that you added
It looks very much like the one that I fitted to my wagon.
I would say you have the right one, good luck.