funny this topic should come up.
I'm going to replace one of the chrome strips on my rear door tomorrow.
bottom line, yes, you need to remove the plastic panel FIRST. After you have the panel off, you'll understand why.
Depending on WHICH plastic panel it is, there is a technique for removing it. Make sure you know the secret before trying or you could very easily end up damaging it.
Once the panel is off, you CAN gently force the chrome strip out w/o doing any damage....this is what I've done.
...then simply reinstall the new/repaired strip in reverse order.
1985 300SD - 'Grace' (198K mi.)
2010 Honda Fit Sport
2013 Honda Accord Sport
1996 Lexus LS400 (Retired)
1995 Ford Contour SE (Retired)
1976 Porsche 914 (Sold)
1972 Datsun 240Z (RIP)