With some cables it's easy with others it's a pita .
With the XS cable it's easier than most . Most meter shops (a dying art) have a device , dies etc that can put a square shape on a wound , round cable . Barring that option the wheel end has a fitting swagged on that the cable "can" be removed from the cable or copied . Due to the nature of the material and its environment I've never had any luck soldering to the cable even with high tech flux and high temperature silver bearing solder . Instead I measure the cable and make the replacement end just a few thou larger . I made a small die to fit in the hydraulic press that was simply a v block with a round groove in the bottom and a matching die for the top with relief just several thou smaller than the piece .
As for shortening the outer . Pick which end you want to attack and carefully cut off wheel the end leaving just enough cable remaining to get a hold of . You will see that turning the cable one way will reduce its diameter as it comes out of the fitting . Most ends are swagged on with a hex die that is usually sold as a cable crimp at an electronics supply or even Radio Shack . In a pinch I slit a cheap socket down the middle and brazed the pieces to a pair of vice grip jaws . ( if I had it to do over again I'd tack the socket to vice grips first and not have to bother with alignment later ) I still have the tool .
The important thing is to end up with the same difference between inner and outer as you started with . This holds true for control cables as well as Tach and Speedo .
Hope I gave you some idea
~kop