See this thread at volvospeed:

http://volvospeed.com/vs_forum/index.php?showtopic=5845&st=0&p=52820&#entry52820

You can do the job yourself, but it's a lot of work. Apparently the best way to do this is to get an engine hoist and remove the engine and transmission through the hood of the car...apparently you can do the change without removing the engine, but experienced people have indicated that it is better to remove the engine and transmission. The procedure is well documented and doesn't require any special tools, but it will take you probably about 10 hours of work....The thread above is good because it discusses how it was done, and other things you should consider replacing in the process.

-Scott