Since one of the things driving this decision is $$$ I think you should get an idea of the respective trade-in values. You maybe trading off larger loan payoff now vs lower loan outstanding on new.
BTW neither car ideal trade-in material IMO and private sale may net more.
Also, from the sounds of it Contour more appealling car for mod investment, but stock Taurus OK for basic transportation (just tint windows so no one recognizes you driving

).