Duplex Tool Post Grinder

I've got a Duplex D27 toolpost grinder. The surface finish from it is far from perfect - I suspect that the bearings need replacement.
The manufacturers, as is their habit, suggest sending the spindle back for rebuild/exchange. I'm naturally sceptical of this practice being a tight git at heart. Has anyone replaced the bearings on one of these? Should be quite simple in my book or am I going to struggle with balance problems for ever more?