Those are individual issues from being 25 years old more than anything
Common 1 for the windows not working is faulty switches, putting 12v directly to the wiring will tell you if it's the motor or the switch at fault, sometimes the switch on the drivers side being at fault stops the passenger window working............French electrics for you
The oil level gauge works from a sensor that's next to the bottom of the dipstick tube on the engine block - quite common for the wiring to be damaged on them or damage to the sensor itself so have a look & see what's going on in that area
Another common problem for the wing mirrors not working is the knob/switch, finding a known to be working 1 is the 1st port of call, 9 times out of 10 that'll fix it but if not it might require a bit of digging around inside the door to look at the wiring & connections in there
The door not locking is a bit of a mystery to me though especially with it working manually - I'm having a wild stab in the dark here but I reckon there might be a seperate wire for each way the doors lock going to the solenoid and there's a bad connection