2007 Nissan Altima Needs a Refresh

My little brother is smarter than is a very few narrow and select ways. He's had the same Nissan Altima he bought right before college for the last 7 years, and before that, one other car. I myself was on ride number 8 by his age (stupid, VERY stupid amounts of money were spent feeding my habit). He's happy to keep this car for a few more years, but wants to restore the car a bit now that he has a real job.

This car has seen about 95,000 very tough college-years miles, but runs fine and has great, fresh summer tires on it. The suspension is pretty beat at this point, and there are blown speakers all around.

My question is, in his situation, with about a thousand dollars, what would Oppos do to restore this car? What is the low hanging fruit, so to speak, in restoring this car, at least in part, to its former glory? Be as specific as you'd like!

Edit: It's a 2.5S