Thanks for all the suggestions. I'll summarize my success (or lack thereof) with each.
Mark---I tried the Replace command as you'd suggested, and after some frustration with the formula showing up instead of the revised text, I finally managed to get it to work.
Tom---Correct. All cells in the column had 10 digits each. This option worked as well, but I had to tweak the formula slightly to insert the second hyphen in the proper position so it followed the xxxx-xx-xxxx format. Ended up using =LEFT(A1,4) & "-" & MID(A1,5,2) & "-" & RIGHT(A1,4)
Mark (again)---This one seemed to be the most straightforward and easiest. (Guess I should've paid closer attention during that Excel training session!) I replaced the zeroes with question marks, copied the formula down through the rest of the column, and there everything was, hyphens and all.
One last question---for each option, the reformatted text with hyphens HAS to be in a distinct column from the original data, correct? Just wanted to confirm, as I can hide the original column and only show the good, hyphenated numbers.
Thanks once again to everyone for their help!
John ("gonnabe" an Excel wiz someday)