Regarding the food, we stopped at a supermarket before we entered the part, but that meant bringing a cooler and keeping it stocked with ice. However, it turns out the bigger rest camps have small groceries, so you could definitely self-cater without bringing anything along.
If you're going with some other people, I would consider driving yourself, because you can pace yourself as you see fit. We did a sunrise game drive, since you can't leave the rest camps on your own between sunrise and sunset, and I didn't like it as much, because we were at the whim of the bigger group. On our own, we could make the call to sit around for a while to see if the hippo we were watching came back up or to wait for the crocodile to make his move on a flock of shore birds. And on the other hand, after a while we'd seen enough zebras and giraffes, and after a few photos, we wanted to move on.
However, if you're going alone, long days alone in the car would bore me, and I would want someone to share the experience with, even if they're strangers. Also, if you're renting a car, the cost will be higher because you can't split it. Our $300 was definitely dependent on two people (and it was actually even less than that, because we were a group of four).
We did tent-camp (which was fun, just to say we were in a tent listening to a lion roaring outside the camp fence at one point), but the range of cabins is impressive, so there are a lot of other options if you don't have the gear.
Also, are the game drives all day or just for a few hours (like the drives organized from the rest camps)? Two full days may sound like a lot, but when there's something worth seeing, it's easy to spend half an hour or more parked in one place, watching or waiting. Plus there are long periods where you don't see much at all.