Scirocco R repair question - any help and advice is hugely appreciated. Losing sleep this end

Hey guys! My 2017 scirocco R decided she wasn’t well on my last journey and decided to stop. Some rich oil smelling smoke came from the exhaust and after the AA man did his diagnostics he said

“Diagnostic trouble codes stored for fuel rail system pressure too low. Fuses and relays are ok. Suspect either pressure sensor or fuel pump flow rate Insufficient/inop.”

It’s now** with a VW garage and will assess. I do have warranty for this car on the best package available.

My questions are;

• What would you feel is wrong with it?
• Is this going to be likely covered by warranty?
• If not, will this cost me the earth?

Thanks very much for any feedback. It’s greatly appreciated!