This has to be the easiest kit I have ever installed. Just coming off Mos Eisley, Diagon Alley, and the International Space Station, this thing was a piece of cake. Honestly, if somebody feels this was fiddly to build - don't ever try any of the three I just finished, they will drive you nuts.
I have the motor kit installed in mine, and the lights fit just fine. A slight modification - put all three interior lights in the bottom side of the top. Some windows are a bit blocked, but that's the way it goes. Wish there was a way to put mobile power inside this thing for when I run the train - lights on while running would be super cool.
After I did the first additional car - I realized there were far easier ways to install the wiring and lights. On the brown part, leave the curved pieces off, that way you can get inside to install that silly white upright. And I figured it was easier to install the expansion board further back in the car, and didn't bother with the sticky things (which, now that I look, aren't even in my kit).
Yeah the instructions aren't the best. I'm not sure what's going on, this is the second set that seemed to miss a few steps. Mostly it's confusing to figure out the intended wire routing path. The wire from the main middle car to the outside cars, would have been cleaner down low. To install the motor system, you have to take the ends off - the wires would have been better in that zone. Removal and replacement of the ends is in the Lego instruction…