It is a shim under bucket setup like a dohc motorcycle. First you measure the clearance an all the valves, then if any are out of spec you pull the camshaft(s) up and lift off the follower bucket and lift out the shim and measure it, then from that measurement you figure the shim thickness it will take to bring it back in specification, then install the shim and bucket and camshaft(s) and check the clearance to make sure it is ok.
If you have done it once it is not that big a deal the second time but it is somewhat time consuming. But is lots easier than doing it on a motorcycle because of all the extra stuff you have to take off on them.
And yes, that is a lot of money for an oil change and valve adjustment, even on a dohc. Doing a Ranger would be fairly quick for an experienced mechanic since the top of the engine is in the open when you raise the bed. But it takes lots longer to do a 570 than a 500, which can be done in 30 minutes easy with time left over to have a beer or two.