1999 GLT - Throttle Position Sensor
 

Is this something that I can fix on my own? Any step by step instructions availabe. I signed up for some e-doityourself repair manual. Basically it provides coloring pages for my kids.

It is inside the throttle body. The entire throttle body needs to be replaced and it can only be done by the Dealer or a shot that can download Volvo software.
If you are in the U.S. there was an extended warranty for 10 years 200k miles.
If you are out it will cost like 1K to get it done.