the door panel is not particularly hard to get off and back on,. but you need to look at the instructions in the factory manual or on this forum, so you avoid breaking anything. Once you get the fasteners out, you lift up on the panel to disengage it. There are plastic hooks moulded into the door panel backing which hook into holes in the steel door. if you break one of the hooks off the panel, superglue it back on. the upholstery panels are well-designed and are quality stuff, compared to the cardboard and push fasteners we used to get, and most other car makers have adopted some of these design features.
The driver's inside door handle is a normal wear/ failure item and is readily available, either in a salvage yard (but it is probably worn, too) or new. Overall, the door, window, et al, are not as hard to repair as one might imagine. patience, grasshopper...

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Providing a home for these cars:
1951 Buick Special De Luxe
1977 Rolls-Royce Silver Wraith II
1970 Rolls-Royce Silver Shadow
1986 Mercedes-Benz 420 SEL
2005 Mercedes-Benz E 320 CDI
2012 GMC Sierra 1500 4X4
1927 Pierce-Arrow Series 80
1931 Pierce-Arrow Series 43
1926 Ford Model T coupe