318i: rear U-joint is sqeaking...now what?

[topnotchraly]

As it says, on my 97 318i, the u-joint right in front of the differentions has started to sqeak. Curiously, it only does it when reversing or on 'over run' (coasting with the car in gear)

What does it take to replace it? Do I have to change the whole drive shaft?

Thanks.