That does sound tricky! No wonder you are concerned.

I can't speak from experience but intuitively it seems that avoiding a really noxious pain stimulus is a good idea. Having noxious pain seems like more of a risk to me than going off LDN temporarily. It has a short half life, so should clear your system pretty quickly before surgery and the worst surgical pain is in the first 4 days usually. So maybe a week off it?

The LDN is working by modulating your immune system and down-regulating glial cells. It took it a while to do that so I would think relapsing back might take a bit of time. If your doc is game they could put you on the antibiotic minocycline 100mg 2-3 times a day for a week. It is also a glial cell modulator and is given post-op to decrease neuroinflammation. I could dig up an article on this if you need.

As far as pain meds, regular opiates increase glial activity and sensitization and should only be used short term. If you do okay with tramadol it will act on both opioid and NMDA receptors (ketamine acts on NMDA). When I had my surgeries I took opiates less than 4 days then switched to tramadol.

These are just my thoughts for what they are worth. Sweet deal on the Vit K infusion during your procedure. That's a great plan.
Sending hugs and healing love for procedure day,