I am replacing the A-pillar trim and am wondering - should I A) put the 3 metal clips on the chassis body and snap the plastic into them, or B) attach the 3 metal clips to the plastic trim and then snap it into the metal chassis? What is the safest way to avoid breaking the plastic trim tabs?

 

 

 

100%, the finisher clips need to be pre-mounted to the plastic A Pillar before install.
You might find this video useful > https://www.roverparts.com/resources...llar-moulding/

 

 

Put some grease on the pillar where you attach. Maybe even separate the clips a little. This job is harder than it has to be.