If just installing the LSD unit into your existing CWP, then it shouldnt be too difficult for any competent mechanic.
Dunlop Auto's in Bangor specialises in Gearbox repairs, I'd be certain he could do it, mention "Big Andy" sent you
Turkington Pitstop fitted my LSD on mx5, it was a good few years ago but Les did it no problems.
Probably bolt in job with housing and all? This will be pulling the diff out and pulling it apart and changing the internals so a bit more involved setting lash, etc.