How to Replace the drive shaft on my Kenwood Gourmet FP505?

The plastic cover on the drive shaft of my Kenwood Gourmet FP505 has split making it difficult to attach and remove accessories as the split has increased the size of the shaft and the items are hard to push on and to get off. The motor still works fine. I have found a drive shaft replacement which I can buy but am not sure how to replace it. Thank you in advance for any help. Julia