Just drop the kick panel under the dash and take off the cover plate to the right of the gas pedal. The car is driveable like that, no problems. That gives you a nice inspection point to look at the bottom of the heater core.

It probably is not leaking a lot now, but it will. You do not want to take off the heater lines to the firewall, that is a painful procedure! But removing the core is easy. There is no need to remove the glovebox either, as per volvospeed. If you are as slow as I am, 4 hours start to finish. Have a plastic baggie without holes to catch any coolant that will dribble out of the lines :)

Ditto on brakes/rotors. A very easy job. The only complaint I have is from the UPS delivery guy because of the weight of the rotors!!! If your rotors don't have a large lip on the outside edge, the rotors probably don't need to be replaced.

Klaus
--
Proud owner of a 220S. If I had more room, I would have more Volvos.

You've probably got the classic leaky heater core...they all leak at some point, mine included. Feel the carpet under the footwells. If it is wet, you should probably go ahead and replace it. Between these and the evaporator on these things, the climate control is a piece of junk.

It looks like a pretty easy job on these cars - there is a write-up for you here:
http://volvospeed.com/vs_forum/index.php/topic/9717-pics-of-heater-core-install/

Order some new O-rings to connect at the firewall while you're at it.