Looking at the ROEM site the cable comes as a complete unit ie the bowden cable with fittings either end so it will be a case of removing the old cable (outer and inner) and fitting a new one. Looks like a complete vehicle lift and/or a pit will be required to remove the old cable and reroute the new one. A new cable, part number 34416785397 is priced at around £25. Looks to me like BMW would take about 1/2 hours to fit at current hourly rates. Perhaps there are others here who have done it themselves and can advise you on fitting.