Another Berlingo Problem - oil leak and boost

[Oldbhoy88]

Hi All, My van (berlingo 2014 1.6) passed its MOT but came but with a bad oil leak. I suspect the cam shaft gasket is away as the oul seems to be below the rocker cover gasket. But today, my van seemed to lose power/boost, driving up a hill. The engine management light has come on. I plugged it into my machine and code the error code P0243 - Turbocharger wastegate actuator 'A'. Do you think this is connected to the oil leak? Is it a big job to change the gasket, or does anyone have any advice? Thanks