well it CAN be done for around a modest $25,000.
look up a company called HPA Motorsports.
www.hpamotorsport.com they do AWD conversions on VW/Audi products- look at the $ and that should give you a basic idea on cost. how about $60K for an AWD Golfzilla??
bottom line- it can be done for a LOT of money- and whatever shop is suckered into this mess have fun- I wouldnt touch it with a ten ft pole.
(PS. even in an AWD car you cant launch at 6500 RPM's- its called drive train- you have twice as much now and you can do some serious damage to your car doing this.)