Cam sensor replacement 2008 1968cc TDI PD

Hi,

I have an intermittent Cam sensor fault and occasional cold start problems.

I'm getting a lot of confused info.

Are there two types two engine types  one with easily replaced cam sensor and one that requires cam belt removal.?

If so how do I identify the engine type?.

Also I read a topic that suggests that that cold starting is caused by a problem with the crank sensor not the cam sensor.

Is the cranks sensor easy to change. I don't want to be paying loads of money to change the wrong thing.

The quotes I have had are £134, £350 and £600 depending on what needs to be done.

Some expert advice would be appreciated.