Puzzling through some leaks, installing electronics and sometime soon (hopefully) pulling the mast to re-do lighting rigging, and a host of other stuff. I posted some questions about my headliner woes in the forum and as expected, got helpful...
YKK Coil#5, in beige, purchase here: https://www.owfinc.com/
StarBrite Snap and Zipper PTFE lubricant, patience.
I never needed to rip any seams, but I did pull some adjacent liner staples.
Once I was able to remove the old encrusted heads and separate and lubricate the teeth, I could choose which end of the zipper from which to begin my new slide path.