I just got finished replacing the fuel filters on my new to me 2018. 27K miles. Fairly straightforward. The filter under the truck is the same as the fuel water separator. I hooked a hose to it to drain it. I drained more than 3 quarts of fuel and thought it was never going to end so just started loosening the filter. Even more poured out before it was finished, probably close to 5 quarts total so be prepared.
After that, you have to remove an "L" shaped skid plate with 4 bolts covering the filter. It is either a 14 or 15mm socket with blue loctite so use impact if you're lazy like me. The filter removes with a 1-1/4" socket. Lube the o-ring and install the new one.
Under the hood, the smaller filter is fairly easy, although you have to climb on the engine to reach it in the back. It's right on top behind the plastic top engine cover. There's a clamp with an allen head bolt (5mm allen) to loosen the filter. The fuel line clips don't require tools, the right side has a safety clip that slides to the left and then two black buttons to release. The left side just has to black buttons to release. A little fuel will spill out so make sure to have rags underneath the lines.
Make sure you pay attention to the orientation of the filter, it points the opposite of what I expected and had to double check with the old one. It flows from left to right (passenger to driver).
Put everything back together and do a "key on" cycle several times and check for leaks. I was able to hear in the garage the pump pushing air out of the filter each time I turned the "key" back on (button on my Lariat). After several (maybe 6?) times I started the truck, it turned over maybe one more time than normal before firing up.
I hope this helps someone, there's not much maintenance info yet for these motors but I'm not good at trying to make a youtube video so text it what you get.
That sounds somewhat reasonable for a dealer price. I paid ~68 before shipping for the filters on dieselfilters.com. Part number is FD-4627 so add dealer markup and an hour labor and "shop fees" and that sounds about right.
I'll have to get some better lighting to take photos but that one photo shows where the one is on top of the engine. If you pull off the plastic engine cover it is right on top near the firewall.
The one under the truck is maybe a foot or so forward of the fuel tank behind a "L" shaped skid plate. There is a hole to drain from the filter since this is also the fuel water separator but to get the filter out you have to remove the whole plate.