Something to keep in mind, and I know this isnt going to sound very good, but it is important:
If you find yourself getting really scared when you're getting behind the wheel... dont drive. Why? Because it's a type of distraction, and a nasty one at that. You're much more likely to make a mistake in that state.
You need to build yourself up to something like this SLOWLY. For example, when I originally learned to drive, I learned it in mostly empty parking lots. Nice and slow, so if I did hit anything, it'd be a light "bonk" rather than a full crash. Doing this until you've gotten comfortable with controlling the car is a very good idea. After that: Blank country roads, preferrably. The sorts of backwoods roads that nobody ever seems to use. This lets you learn to move faster, without having to worry about piles of traffic. It's also much less annoying.
If you do live in a crowded area, consider finding someone who is willing to take you to places such as these. They are safe places to learn and practice.
One way or another, there's no way around the fact that driving is dangerous. People tend to underestimate it. I've been driving since.... 1998, I think it was. I seem to spend alot of time in the car. But back then, I sure wasnt perfect. And since then, I have indeed had a couple of accidents. One was because of ice, because screw winter. Another was my own fault, and a third was because some blazing moron put some gigantic bushes in a seriously awkward position at a particular intersection... I remember the police guy telling me "Yeah, we've had just one crash after another at this exact spot" and I'm thinking.... Just get rid of the freaking bushes and it wont happen anymore! I never got hurt in these (except one where the airbag deployed, and scorched my wrist a bit due to friction, but that was mostly just annoying), but the cars sure did. One crash was like something out of a comedy reel; I ended up taking the car to a repair place afterwards... but the front part of it, the big that has the headlights on it, had been torn off (wheras the internal metal parts or whatever they're made of, which are the actually sturdy bits, were fine... it seems to be the outermost parts that are easily damaged, which is probably why cars can be dented by really stupid things like shopping carts) and was sitting idiotically in the backseat. Must have looked absurd. Another crash simply demolished a different car I had at the time.
But I remember a very important saying that someone taught me as I was learning: "If you fall off the horse, you have to just get right back on, right away". And that's true. You cant go around all the time constantly worrying about what MIGHT happen even if something has already happened. Just learn from any experiences you have, positive or negative, and you'll do fine in the end.
Just... dont go near highways/tollways until you've had alot of experience. Trust me on this. Even some people that have been driving for a long, long time avoid those like the plague. But something like country roads? They're fine. As long as you watch the weather, they're downright pleasant places to go. I sometimes go wandering around them just for the heck of it, finding new roads just to see where they go (I have my phone, AKA my magical talking map, for if I get lost, so it works out nicely).
Yeah, it's scary at first, and driving is inherantly dangerous in some ways... but so are so many other things that we often do frequently. Learn slowly, practice in easy places, drive safe, follow the rules, and really, you have little to worry about. NOT doing those things is what causes the majority of crashes.
And you'll learn to deal with the sensory bits in time. Honestly, I think EVERYONE gets a bit overwhelmed at first, with having to deal with loads of stuff at once... it aint just people with autism. Equally, things like issues with depth perception and that sort of stuff can also affect anyone. But to some degree, it's not necessarily a problem with you... some of it is just inherant to learning these things. I had a bit of that issue at first too. But now? Not only is the issue gone, but I know *exactly* where every part of the car is in relation to the road. I remember one time, I come around this corner to find a huge pile of... some sort of tiny animals. Must have been crossing the road. No time to stop, so instead I simply moved somewhat to the side, putting the left tires BETWEEN the animals (they were more than small enough to very easily fit under the car) and the right tires PAST them. Indeed, I did not hit any. They all were unhurt. That's how accurately I know it at this point, and I have just as many funky sensory issues and such as anyone else here. If I can learn that, you can too.
Whatever you end up doing, good luck to you. You'll get it eventually... just be careful, take it slow, and dont give up.
