Hi can anyone help please? I have an audi A6 2.5 TDI, there is a leak from the sump, i need to remove and re-seal, is this very difficult? I have been told i have to remove the front subframe?

Also, my car has been chipped, i notice when i am driving it, when i rev over 3000rpm, there is a tappety noise coming from the engine, could this be the tappets or maybe the big end??

Thank you very mych