If you have the tubing and 3 jugs, and a thin necked funnel, then it is time to flush:

Remove the air intake hose that goes from the front to the air cleaner. Pull off the hose at the air cleaner first, then just pull the hose off the top of the radiator. Easy.
Remove the clamp on the hose to the radiator by pulling it apart and pushing it and the hose away from the radiator. This is the top hose on the driver's side, for the tranny cooler.
Slide your tubing over the hose and put the other end into a gallon jug. Place the gallon jug where you can see it from the driver's seat.
Remove the dipstick from the tranny filler tube and leave it where it won't get lost.
Turn the engine on and watch the old fluid drain into the jug. It is real quick, so when it almost gets to 1/2 full, turn the engine off. Add 2 quarts of new fluid through the tranny dip stick tube. It's slow... Then repeat until you run out of new fluid.
Button it all back up. You are good to go.

For the PNP switch, take a look at this: http://volvospeed.com/Repair/pnpswitch.php

You can buy a PNP switch at Autozone, if you are cheap enough!

Klaus
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The 164 has a new home, all I am left with are a 95 854T and a 98 V70R :)