You don't have to take it off to clean it, it just makes it a hell of alot easier. If you just take your intake off you can get to it, then it's just like 3 or 4 bolts that hold it on. You can clean it without taking it off though. Spray some deep creep or other type of throttle body cleaner into it (behind the butterfly), let it work for 15 minutes or so, then use a nylon cleaning brush to clean the carbon off. It'll be a little more challenging with it still on the truck since you have to hold the butterfly open, but I've done it twice.
Up to you. Not gonna hurt anything if you don't clean it out, but might boost your mileage and throttle response a little if you do. It all depends on how dirty it is to begin with.