Great resources, Claire! Thank you.

Not after you place it… unless it’s linked.
You can link Word docs (see the article below), but most people usually do not.
https://indesignsecrets.com/import-word-documents-edit-in-word-and-indesign-and-keep-linked-for-updating.php

Ann, I don’t think you’ll find any problem opening your CS6 files. It’s possible that there will be some text reflow, but it usually isn’t significant. (See link below.)
But yes, you absolutely will want to update plug-ins and some scripts to new versions.
As for will you find your way around? I don’t think you’ll have much trouble… the vast majority of the app is the same, though there have been some UI differences. I’d read over the links below to get up to speed.
https://indesignsecrets.com/indesign-cc-2014.php
https://indesignsecrets.com/indesign-cc-2015-available-shading-graphic-cells-more.php
https://indesignsecrets.com/whats-new-with-indesign-cc-2017.php
https://indesignsecrets.com/whats-new-indesign-cc-2018.php
https://indesignsecrets.com/whats-new-with-indesign-cc-2019.php
https://indesignsecrets.com/whats-new-with-indesign-cc-2020.php
https://indesignsecrets.com/opening-old-documents-in-indesign-2020-can-cause-text-reflow.php

Hi Katherine, This is a fascinating question… the problem is that features such as grep styles cannot see where on a line text is… for example, you cannot say “find all the spaces at the end of a line.”
However, scripting allows this. A number of years ago the scripture Jongware wrote a script to remove all the underlines at the end of lines. Very similar problem. You can see that thread here.
So I took that script and edited it slightly to remove strikethroughs. You can download the RemoveStrikethroughs.jsx script here by right-clicking the link and saving the .jsx file to disk. (If it gets saved with .txt at the end, then remove that… so it ends with .jsx.) You can learn how and where to install the script here:
https://indesignsecrets.com/resources/faq#145
Once it’s installed: Select the text you want to apply it to (with the Text tool), then run the script from the Scripts panel. All the spaces at the end of lines will have a character style applied to them… and that style (called “NoStrikethru”) will remove the strikeout formatting.
If the text reflows, you may find those spaces in the middle of paragraphs (with no strike through). So you may have to reapply the strikethrough to those, and then run the script again.