... just picked up an '04 XT... What should I look out for? How do I maintain it and keep it in tip-top shape? How do I clean it?
Open the roof all the way, clean the tracks if needed, and lube them with silicone or lithium spray.
I think some roof motors and mechanisms fail because some people operate them a lot, and park under trees with the glass half open. My trees drop all kinds of things all season long. Seed covers, seeds, pollen, and leaves. If they fall on a car top, they don't stay long. If they fall onto a half-open moon roof, they cannot escape and are blown to the edges and back under the roof. You may never see the stuff. Over the years this material gums up the grease in the tracks, increases friction, and strains the linkage and the motor. Jams and breakages can occur.
I use my moon roof sparingly, and don't park with it half open near trees.