I need to remove the rear door panel of my 1996 Honda Passport. How do I do that?:(

I drive a standard transmission 1999 Hyundai Accent GSI. I commute over 200 kms a day so this vehicle has very high mileage...close to 200,000 kms. It has an aftermarket car alarm installed and also an aftermarket cruise control which doesn't work. Anyway, over the last several months I have noticed a very odd power fluctuation while driving. It happens several times a day while driving or idling, and it happens in any gear. All at once the following things occur: The radio or CD that's playing will cut out but not lose power; the car feels bogged, like it's driving through a deep puddle; the RPMs do not change at all; the fan, if it's going, suddenly gets louder. It usually lasts between 5 and 30 seconds and then it stops. My car also has an air vacuum gauge on the intake manifold and that also does not change during this fluctuation. When the radio/cd goes off, it still has power because the digital display is still lit up. Also, I recall it happened once at night and I think my headlights dimmed. This car has never broken down or had mechanical repairs previously. My fiance is a helicopter mechanic and is very handy repairing cars, but not so knowlegable for diagnosing this problem. Does anyone have any idea where we should be looking to solve this problem? Any advice is much appreciated.