[EC900]

Depends how all the other paint is holding up, dings, scratches, chips, etc. I’d keep as much or I paint as possible - and for sake of provenance document the repair area for future stewardship.

No need to do entire side (door, ft. fender and lower rocker). Shading is always a concern - but it’s the passenger side…less likely to be noticed every time to go for a drive.

If it were mine…I would just have the previous shop repaint just the bad area if confident in the color match and application talent.
The good thing is they can respray the entire quarter including along the C-pillar and roof line under drip channel, and down to bumper/rocker line. That’s the section I’d get estimates for. All one big uniform color match rather than just the small affected spot.

Seen a lot of quarter panel paint failures in that spot on the Mid-years, mostly the 70’s. Poor paint probably, recall GM had similar delaminating paint problems too.