"Since the files I imported to eMClient are still on my WLM program, and in the correct order, can't I just uninstall eMClient? If so, what do I do with the screwed up files--just delete them?"

Good to hear that you got your Live Mail exported to new computer ! If you're happy, I would just use TB on the Lenovo and uninstall eMClient since the files are not what you can work with. I would then either just delete the screwed up files or save them in a folder for 30 days in case you decide to reinstall and try eMClient again if TB does not meet your expectations.

If Live Mail is still functional on the HP, leave it and TB be for now until you are totally satisfied with the new mail client. You found the calendar add-on for Thunderbird (Tools tab/Add-ons) ? And check your address book. Like I said, I had to go back in and update birthdays and some phone numbers which the 'People' app fortunately had from syncing with the win10 Mail app (another reason I have both that I forgot).

Mark your topic Solved if you are happy with the problem resolution so others with your issue can find by Search. Cheers.