Trying to buy a used car but Dad won't budge. What do I do?

I've found a 2003 Nissan XTerra that I have fallen in love with. The dealer wants to finance it to me for $9,890, no interest for 18 months since I'm putting five thousand down. However, my dad doesn't like it because of it being top heavy. He thinks I'm going to flip it or something. I see his point but at the same time I know better than to turn a corner at 50 mph. I need a car like this for work and I'm about to go to college in the mountains. I think that this is the perfect car for me. What should I do?