I think the other guy answered your other questions. There are a couple of screws on the black moulding part under the passenger side windsheild wiper. Just undo them and you can lift the flap up and see wehre the filter is. It's a tight fit, but you'll be able to wedge the old one out and a new one in. I highly recommend the charcoal activated one to be used in the winter time...a lot of nasty exhaust will "try" to get into the cabin from driving behind trucks, etc., and this particular filter makes a huge difference.

In regards to the Auto Dimming mirror. I took the OEM out of my S70 and installed the one that comes in your car. The green light is normal. The other side that looks like a burnt out light is the light sensor. It is what senses bright lights and dims the mirror, so it is normal for it to look burn out the way it does.
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1998 S70 T5 Emarald Green Metallic, 2004 V70 2.5T Ruby Red, Previous Owner of Black '94 850 Turbo Wagon. My cars have been running so well lately they've got me worried.