At least here in the U.S. and I assume some similarity in all washing machines, it's a pretty serious job to replace the drum bearings.
First thing, though...best way to check for a failed drum bearing is to remove the drive belt and rotate the now free drum. A failed drum bearing will make a rumbling sound while the drum is rotated. If that's the case, unless you're a really serious DIY'er, I'd call a repairman. Firstly, just getting the correct bearing and seal can be a duanting task, since the actual washing machine brand name is often made by a third party manufacturer. Secondly, with the newer, often plastic tubs, the beraing is pressed into and sealed in the bottom of the drum, making it likely that you'll have to replace the entire drum. (You didn't say if it's an upright drum or a horizontal one).
If you have the model number you can often go on line and find a video of how to do the job...