The drain is on the drivers side (Left hand drive) of the radiator. I did this recently and I took off the plastic shroud, but you might get by without. I removed my shroud since I had no idea where the drain was! Shroud removal is pretty straight forward.

When I drained my system, I all I could from this valve was about 1 gallon. The system holds anywhere from 2 gallons to 2.25 depending on who you listen to. My manual did not provide a quantity since it said the change was not necessary! Anyhow, I drained what I could and replaced it with distilled water. Ran the car a few miles, and then drained again, to repeat this process 4 times (collected 4 gallons). After draining that last time the fluid was still a very pale green, I topped off by adding a gallon and a little of the Volvo OEM.

A few cautions to mention. I was doing this on a hot system, and could have gotten burned easily, but I've done similar things before and was pretty cautious. I was also concerned by adding the cold fluid to a hot system and worried about warping something with the sudden coolness of the new fluid, so I added fluid in small increments.

Good luck, let us know how it goes!

Jerry
01 V70 T5

If you mean the air guide that is held on with 2 10mm screws, yes. Be careful with that plastic plug. It might be easier to take off the bottom hose from the engine side and let the coolant pour into a large catch pan. That will drain the engine and radiator at the same time. Just make sure when you put the hose back on, the clamp is in the same position on the hose before you took it off.
Also a very good time to replace the thermostat with a new OEM version. Invariably, they break about a month after you do a flush :)
Get a new cap for the expansion tank and buy 1 gallon of Volvo antifreeze.

Klaus
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Just driving a 1998 V70R :)