Wow, very quick replies, and helpful and polite, too! Thanks, guys! Turns out it was the .dll file. I looked, and there was none, so I deleted the TAC Life Support data and re-unzipped the file. There was still no .dll file. So I deleted the .zip, went back to the download link (same link as before, linked from the Scott Manley Interstellar Quest mod list), and this time there was a .dll in the contents of the .zip file. Haven't used it in flight yet, but I got the dialogue window Scott did in his videos this time upon launch of KSP. Thank you so much!