I just replaced mine. Broke right before hitting 160,000. I wasn't that scared to mess around with the dash, as I've replaced the AC evaporator and this was a piece-of-cake compared to ripping the whole thing out!

http://www.matthewsvolvosite.com/odometer_fix.php - Here's the pics I followed.

I had a friend hold the dash up while I slowly guided the cluster out. Don't force anything and make sure that all the cables (two on top and one directly in back) are disconnected first. Mine has a vacuum line for the cruise control that had to be disconnected. Make sure you have a rag in place as you guide it out. You don't want to scratch the front of the cluster.

I had to purchase the gear from Marin County Volvo. It's about 1/2 the size of a dime and cost "only" $35!!! I found the 3v bulbs (yes, change them now) at a local parts store and only paid $12 for 4. Marin Volvo wanted $6 each. The two bulbs that light the digital display were also $6, but these were only available at the Volvo dealer. I had to use a photographers lupe to look at each bulbs filament. They are very small to see with the naked eye. A magnifying glass should work.