I’m about to give this a go (with another car forum!) and I’m going to ask for help. 
Is your script in your last post a drop in replacement for the last step from the first post? I’m trying to make sure there isn’t more involved that I need to prep for. Understood that I need to swap out the Renault related items. The execution steps you have in the top comments seem to suggest so. I’m going to read the entire script so I understand what it’s doing. Probably have to make sure more than the attachments path is going to the right place. We have a substantial Media Gallery.
Short answer : Its depends.
Longer answer : I didnt do much of the setup from post 1. I had to do some work with gemfiles. Thats it.
Both my XenForo and Discourse were on the same server. That means that you can link the shared area of the discourse container to the Xenforo areas. That made my life a lot easier.
I didnt bother exporting my Xenforo DB either as it was on the same host. No benefit from doing another export.