Just search around for "door handle carrier replacement"; it's a common failure point and there are a couple of excellent writeups on replacing it. I replaced the passenger-side carrier on mine last month, and it went pretty smoothly; took about an hour or so. Most of the work is just getting the inside door panel off; once that's out of the way, the rest is really easy. The part was just under $100

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2001 X5 Sport 3.0/5-speed
1998 318ti/5-speed
1988 735i/5-speed
1984 528e/5-speed (soon to be M20B25-powered 525i!)