Ben,

Pretty much a straight forward job. Don't put any kinks or sharp bends in the new cable when installing it. Look at the old routing before pulling the old one out. You may want to dust the drive cable with a bit of powered graphite to help lube things. You'll need to remove one Allen head bolt at the tranny end ... get the proper size key/wrench. There is a little umbrella like seal at the tranny end. You may want to have a new one on hand when you install the new cable. Get the right lenght cable for your application. As I recall they do come in several lenghts. Groton and Import Parts Specialists are very good places to order quality parts at the best prices I've found. You can save a very large amount of cash buying from these folks as opposed to the dealer. Plus they are nice people. Don't always find that at the Volvo dealership.
Good Luck and have fun.

http://www.fcpgroton.com/volvo.htm