TDI PD115: Timing Belt Change - What to Replace?

Hello,

What would you replace while the timing belt is being changed on a BMW M3, especially since so much needs to be disassembled anyway?

Timing belt...
Tension rollers...?
Timing belt...?

What about the water pump specifically? Should it be replaced immediately, or not? Are there any other parts that might need to be checked?

Best regards,
Ralf.