time to get new mondeo

[toyota lexcen]

Hi,

have run up 320K on 2013 Mondeo LX petrol 2.3L

looks like have gearbox leak or engine leak

been to drive the 2017/18 diesel and petrol version

the petrol seems just as flat as my current car but familar with servicing petrol

having never had diesel, can i service car at home, DIY?

thanks for any info