It would also be nice to sell it within the next 400km - once it hits 200,000km you'll lose some more $$$$.
Have it as clean inside as a whistle, smelling nice, polished so it glistens, Bert Kampfert playing quietly on the CD and parked against a background that compliments the colour of the car. If potential buyers say 'but its got a fuel-burning V8!' just say 'well, its a Calais and they're considered a luxury car with a powerful smooth engine. Economy is secondary if you want the best'....or something like that. Good Luck.