Hi, I'd recommend looking at this website http://www.clayraku.fsnet.co.uk/index.html
... the site owner has photodocumented some of his DC04 escapades including clutch and motor changes.  I wouldn't recommend this job for everyone - on a 'DIY engineer' difficulty scale of 1 to 10, in my view dismantling a Dyson to this level is about 6 and reassembly is a 8.  How this was ever engineered for high volume manufacturing I will never know.  You will also need star drives to dismantle the housing.  Good luck
                
 Mark Young
                
 June 2005