I'd be interested in having a look at one of these too, having just bought a recalibrated one myself.
However I doubt a manual has ever been made public. I think that the only place where repairs and recalibration is possible is X-Rite's head office in Grand Springs, MI, so I'd guess that any repair references are just internal documents. Whilst they still offer a repair and recalibration service it's highly unlikely they'd consider releasing any documents, if ever. Unfortunately X-Rite don't seem the most helpful of organisations, so unless a friendly technician emailed you the documents you'll be stuck.