You wouldn't be able to service it well while mounted on the truck. You need to be able to hold it, tilt it, admire it and such. Sorta like trying to rebuild a master cylinder while on the truck. Technically, it can be done, but you do yourself no favors by trying it.

Don't remember the various wrench sizes required off the top of my head, but I can say with certainty it's metric. Though in the larger sizes you can often make do with inches.

Don't remember the exact count of the various components, but it's really only a few. A dozen at the most. It's not daunting once you remove it and open it up.