Hi on the fog lights. The installation is very straightforward. I have some documentation I can send you too, if you'll send me mail at dpsam@sbcglobal.net. Getting the lights in place is easy. Just look for the bosses behind the air dam that take the screws for the brackets. You will need the proper grills with openings. When you are under the air dam putting the lights in you will see the plugs hanging right there behind where the lamps mount. They are the same plastic plugs with the little wire bails that you see all through the engine bay and should be secured to little brackets--not really plugged in to anything. On the switch, no, a rear fog light switch will not work, the receptacle will be backwards. The darker front fog light switch from an 850 will though. They aren't expensive new, but check erievovo.com for a used one. There are two pieces you need under the dash. One is the fog lamp relay itself. It goes in position #201, upper left on the relay board under the dash. You don't have to use the Volvo relay, any standard one will work. One thing though, you have to get the type that switches both output contacts the same direction. That's because one contact is for the light in the switch. If you get the relay that opens one contact while closing the other, everything won't work. There is one more piece you need. In relay position 213, lower left, there are a bunch of contacts that determine when the lights can be on depending on the market. That is, on with headlights only, on by themselves, on with park lights, etc etc. There is a relay-box that goes in there. It's not really a relay, it's just a jumper. Thus, you can make your own jumper. Connecting terminals 4 and 3 gives you US spec, fogs can only be on when headlights are on. More details on the document.
Regards,
Dave