Nissen fundoplication needs to be redone, can it be reversed/taken down instead?

Yes: Technically should be possible to take down and reverse nissen, even laparoscopically. The important question is why it was done and what the reason for wanting to have it reversed. Talk with your surgeon. A seond opinion may be helpful to assess the problem.

Re-do Nissen: Revision fundoplication is more involved than the primary operation. The reason for revision needs to be identified. Recurrent reflux and difficulty swallowing are common reasons. Preop testing should include endoscopy, barium swallow, and possibly ph probe, manometry and gastric emptying studies. I do not recommend simply reversing as it will result in severe reflux symptoms in most cases.