I can tell you it can be a pig of a job - I also had the 'larger' alternator which took a bit of fettling to fit.
Sadly I did it from underneath, which meant removal of all sorts of bits and bobs.
Top tip for ANYONE reading with a CDTi - do NOT let anything drip onto the alternator, be it PSF or engine oil when doing an oil/filter change.
Keep your alternator clean, and lots of power you will glean.
