Car Mechanics Magazine ran an article on buying second-hand Rover 75s a while ago, the message was stay away from the V6 if nearing 60k because the cambelt change is a 7 hour job.... in a garage! It's anyone's guess how long it would take as a first-time DIY job...

Apparently the V6 is very tight squeeze in the 75 (sideways Vectra-style - it's FWD) and lots of dismanteling is needed before you actually get to the belt. They also mention that the timing kit is essential, but this is a more common issue.