If your machine is a couple of years old and/or used a lot, the problem is more likely to be that the bearings are gone - rather than a problem with the drum shaft.
To check this, open the door and put your hand in under the top lip of the opening. Now try moving the inner drum up and down. If it feels like the inner drum can be moved independently from the outer drum then you will need to replace the bearings.
Unless you are very good at stripping machines and putting them back together, I would recommend getting a qualified person to replace them.
It is not impossible to do the replacement yourself but it is very difficult and requires you to take the drum system out of the machine, separate the inner and outer drums, and remove and replace the bearings - then put it all back together again.
Good luck.
Andrew, August 2007