The passenger side interior door handle on my 2000 C3500 was broken when I bought the truck used. I replaced it with an aftermarket handle that I got on eBay, and even though that door doesn't get much use, it broke again a few years later, so I got another aftermarket handle. Shortly thereafter the driver side handle snapped off, this time I got a chrome aftermarket handle, which actually seems way sturdier than the grey ones. Now the exterior handle on the passenger side door is cracked, but still works. I've got an OEM handle brand new in an unopened box waiting for me to get around to installing it. Before I do, I'm thinking about getting a chrome passenger side interior handle to match the driver side one, since I'll have to pull the door panel off anyway. As for where these door handles fail, in my case the crack always seems to be far enough inside the door panel that you can't see it. Before the driver side handle snapped, I could feel it flexing, so I wasn't surprised when it eventually gave up. I'd already bought the chrome handle, so, as my wife said, it was time for me to finally get off of my butt and install the damned thing...
Thanks for the response. It seems like the overwhelming majority of people with this issue have had the handles crack out of view inside the door panel. I'm glad I went ahead and ordered a new OEM handle.