Power doorlocks, windows, dash lights & security system have quit working on my '96 Nissan Quest

Sounds like maybe you have an aftermarket alarm installed on the vehicle? If so, disable this first. If you do not have an aftermarket alarm, then hands on testing of the related circuits is needed. Has the vehicle had the windshield replaced? If so, sometimes a water leak could be present allowing water to hit electrical components under the dash. A wild guess but something I've seen before when weird electrical stuff happens. Check those areas first. For hands on guidance, reach out to a shop near you. https://repairpal.com/auto-repair-near-me Click the link or call us at 877-913-1554. We'll gladly find you a certified RepairPal shop in your area.