Mates Focua C max has broken down.

It's a 1.6 tdci auto, basically when put in drive it makes a noise and only goes so far before it loses drive.

The car itself is a nice motor to have as a daily hack.
I've asked him if he would consider selling it to me, which he said he would consider.

Need to know what the damage would be worst case scenario and if this is a common fault with a common fix?

Thanks in advance