Oddly enough, I live in an even older Ford Fusion and it's really easy. Spend time at the Library, Starbucks and get a gym membership for showering. I work full-time and don't dick around with washing dishes or anything. Got an inverter and think of my car as a generator with wheels.
I took out my front passenger seat so I can lay down to sleep. Made it through the summer in the south and it was pretty bad, but you sleep while your body sweats and you deal with mosquitos and flies on the regular.