the g60 flywheel and vr6 clutch wont work on a 6 speed box, if it is slipping then the more you leave it then the more damage its doing to the flywheel, if you catch a slipping clutch early then you can get away just replacing the clutch and saving a lot of money not doin the dual mass.
dual mass is recommended on any diesel engine anyway, lot of vibration without it, its only the pertrols that have no worries..
my dads pd130 passat clutch started slipping at start of last year, still goin strong now, and thats over 20,000 mile since then! its all on your driving style.