Trying to make sense of your post. Sounds like you have 2 issues.
You received a K-1 late, after you filed the original return and now need to prepare and mail in an amended return to account for this additional income?
The balance due on the original return never got paid?
♪♫•*¨*•.¸¸♥Lisa♥ ¸¸.•*¨*•♫♪