jack it up make safe with stands in right places then its a crawl under the car remove filler pipe big hose to get past anti syphon unit ,then with a length of petrol proof hose syphon out as much as possible .
then put as much new diesel in as you can ,fill to top if possible .
the more you put in the weaker the petrol left will be
being a diesel mechanic f4r 35+ years be4r addatives we used petrol in diesel to cut down smoke when taking trucks f4r test and to help in winter start up
do not be conned that you need all fuel system renewing if you truelly have not run engine just replace filters bef4r start up as you fit them put new diesel in them as you go smelly but be ok..
rob h
December 2010