Hi John Narins 

Unknown said:

1.) I could go to the TM and change the preferences to sentence segmentation. Will that affect the already-established segments in any way? Will it affect how and when they're applied in Translation Results?

Each TU will still contain the contents of your paragraph, so even through you switch to sentence based segmentation it will only apply to new work.  This is because the relationship may not be 1:1 for the contents and Studio has no way of knowing how to handle the re-alignment. So you may have this for example:

Four sentences in the source and three in the target.  So if you switch to sentence based segmentation then this TU will still be one TU in the database.  If you opened the same source used to create this then you will have four TUs when translated instead of one.  So you won't get any matches from this... possible exception would be if you're using fragment matching in which case you may still get some leverage.

Unknown said:

2.) I could create a new project with a new TM, import all the files again, and have them added to that new project TM.

You could, but you'll get little leverage as I mentioned above so would have to translate them again.

Unknown said:

Or perhaps there's another way that would be best? Any advice and answers to these questions will be appreciated.

I guess what you could do is export your TM to TXT and then align them.

So I used SDLTMConvert from the appstore to create two files from the TM, one for the source and one for the target and then I aligned them:

http://appstore.sdl.com/app/sdltmconvert/228/

This is an excellent application from Costas Nadalis that is very useful for things like this.

Regards

Paul