Simple: You don't.
If you take off the filter that sits underneath the dust container, you can get an idea of the state of the motor. Lots of black = motor failing.
After 6 years, our DC07 motor finally failed completely (Smoke, smell.)
Having looked at several online spares suppliers, I resigned myself to spending £40+ on a motor, £12+ on a post-motor filter and the shipping and an evening struggling.
Someone told me Dyson offer fixed price service, including bits, for £65, in your own home and with a year's guarantee
As I'd be spending about sixty quid anyway I figured what the hey, I'll get Dyson to do it for the extra fiver.
Put a request in online via the Dyson website on Thursday, got a call Friday morning and had the visit booked for the following Monday morning "between 8 and 1".
The guy came at 10 and in 20 mins had fitted new motor and post-motor filter.
He also fitted a new post-motor filter cover - the old one needed a good clean and I guess that was the quickest way.
He also fited a new clutch and belt assembly (Its a DC07 all floors) "cos the old one looked a bit worn"
He also fitted a new main drive belt
He ordered a new pre-motor filter assembly AND a new cyclone, both of which arrived in a few days.
I've had another look at the same online supplier sites and totted up what we got. It is about £120+ worth of bits.
I reckon that's pretty good and it just wasn't worth getting my hands dirty.
Did that help?
John, March 2008
