This is from my experience with a 2000 S80 2.9L non-turbo.

You will need to buy a throttle body gasket and carb-cleaner or such. And you must be able to work by feeling your way around. Most of these bolts are not visible.

1) Remove the air hoses. wow not so easy. Matter of fact, it's the hardest part for me.
On the air filter side, I ended up removing the 2 screws holding the air metering module to the air filter housing instead. Of course, you need to remove the electrical connector to it. Then pull the whole thing out from the air filter housing.
On the throttle body side, after loosing small clamp on the smaller hose (by using a small flat screw driver, I was able to twist loose this particular clamp) pull it out and tuck it to the side. Wow, not easy again, after loosing the big clamp, I had to try very very very hard to push down as I wiggle the hose to get it off the throttle body.
2) Follow the electrical wire and unplug it from its connector. Mine wasn't like this, but here'swhat Tech said "You might have to remove the bracket on the back of the starter. It will be 2 10mm nuts and 1 12mm screw. That will allow the wiring to come out from the starter." {could it be since mine had the software upgrade that they had removed it to upgrade it? .. don't know}.
3) Very Very Important, make sure you use some clothes to cover the starter +++ connection. I didn't and when I hit it with the ratchet while unscrew the bolt, yup... spark!!!.
4) There are 4 bolts that you need to unscrew to get the throttle body out. I used carb cleaner and a small soft brush to clean it.
5) Now, just reinstall everything. Don't forget the gasket. I held the throttle body near position, then slid the gasket in place. Install all boths by hand first, then make sure the gasket is center. Now tighten them with the ratchet by alternating between them.

Have fun!