Any chance that the instruction images from the first post can posted again? Or a simple textual instruction. The old images are no longer available.

[s]What I do now is select a model and start the plugin. I get a dialog with the selected model in the left list and a empty right list (the 'replace with' list). There is no way to add/select a model to replace the first selected model. What am I doing wrong? (I think I am missing what the first step is "Before replace...".)[/s]

I figured it out. After selecting the model to replace and starting the plugin you select the replacement by selecting a model in the 2D pane.