Welcome to the board, Trevor!
Strangely enough, I'm one of the minority who do not worry about my engine or rig failing. I can fix any motor, and have done so under awful conditions, and keep my 1986 Evinrude Yachtwin 9.9 in good repair. Starts first compression every time. I discovered that the PO's dolt mechanic had assembled a fuel pump spring wrong so that it would starve for fuel under load. On yesterday's first sail of the year it behaved faultlessly. My rigging, although 20 years old, is also in perfect shape. I inspect every Spring and Fall and replace when needed. This spring it was the T bolts and two turnbuckle bodies that were suspect. No, my fear is that things electronic will fail given the hostile environment. So I don't rely on them, but use a paper chart, portable Garmin GPSmap 76C, compass, hand held wind gauge (just for fun), binoculars, pelorus, hand-bearing compass, all low tech. The Garmin is great, but an inexpensive stand-alone. The Garmin, wind gauge and binocs are all dunkable, too. If I were to undertake a long passage, the inventory would be about the same, apart from some redundancy: a spare hand-held Garmin, the sextant and reduction tables etc., but the tools would be the same. GPS for lat and long, plot on paper chart.