A quick and obvious check is to be sure the wiring harness connectors are all well connected under the helm. I've had problems where connecters were not pressed together tight enough to "click shut" and slowly vibrated loose over time. One came apart just partially on a riding mower once, which could explain why the voltage part works and the trim and fuel don't (if a gang connector was partially loose, some wires could be connected while others not).
If two of the three needle gauges (on one gauge assembly like you describe) quit working, it's highly unlikely that you had a trim sensor issue AND a fuel sensor issue simultaneously. I mean, what are the odds of that? So to me, that points you toward the problem being closer to the gauge and there is probably not something wrong with your motor AND gas tank. That's good news. Probably a cheaper, simpler fix.
My old 2012 SSL doesn't have any fuses, just resettable breakers. If you have fuses, that's an obvious check to make too. Make sure your breakers are all pressed in (that's how mine operate).
