2005 silverado manual side mirror replacement

[Daren37]

I bought a manual replacement mirror assembly for the passenger side door. I cant figure out how to remove the small triangular piece of molding on the inside of the door to access the nuts and bolts to remove my old broken mirror assembly. Anyone out there know how to do this safely so I don't break the darn thing?
I have seen where people advise removing the door panel, but since my truck has manual mirror, doorlocks and windows. (no wires etc.) I don't think it is necessary to remove the door panel located below this small triangular piece of trim of molding. HELP!!!