That truck isn't due for a timing belt for another 30k miles, and the timing belt replacement on this engine is a pretty significant endeavor (there's a very thorough write-up about it in the how-to section of this forum), so you don't really want to dive into that if it's not necessary. Changing the crankshaft bolt is pretty simple really, removing a few items for access and finding a way to prevent the crankshaft from turning when you torque the new bolt to spec would be the only challenges - assuming you have the proper tools it could be done in less than 30 minutes. I'd give it a 3 on a 1-10 difficulty scale.