If your a some-what proficient in wiring, than it's a super easy fix. I re-wired all 3 of my trailer at the end of the season this year. I replaced the 7-way pigtail you're talking about. It would be nice if you posted a picture so we can see exactly what you mean. Click on the link under my signature and go to the last page, i posted a pic of a junction box i made as i re-wired the new pigtail in. It was easy.
As mentioned above, just splice that pigtail right into the trailer wire, avoid any adapters, they just cause problems.