The R56 one should be somewhat helpful:
MINI Cooper R56 Turbocharged Engine Alternator Replacement (2007-2011) | Pelican Parts DIY Maintenance Article, but the Bentley Manual covers the N18 engines in more detail (which is what yours has) and we're having a sale on them right now for 15% off. I'd highly recommend you pick one up:
Bentley Mini Cooper Repair Manuals - PelicanParts.com