Hey retread,
I had surgery and was prescribed pain meds as I went off NAL.
Can you make a few days without drinking?  I couldn't and wound up taking NAL up to the day before I think surgery.  I WOULD NOT recommend that.....I was very lucky though as there was minimal pain and I had arthroscopic knee surgery which for some is hell.  
I would leave AT LEAST three days of no NAL as I took some oxycodone and it didn;t really do much but take the edge off, but again, I wasn't in severe pain...some have said that for opioid block, NAL can last 5 days rendering opiates worthless.  I don't know if that's scientific, but still if I could, I would try and get it completely out of my system.   Others including pharmacists say a day or two,...I don;t know....I also took a Vicodin which did little, maybe it was the tylenol that did something  
 
 Anyways welcome and if you have more q's feel free to ask, My BEst, Jim