Unless the rack is bent from a collision chances are it is a leak. The last 850 I bought had a rack leak and - to my total amazement - Valvoline High Mileage Automatic Transmission Stop Leak fixed it. You can get it at Advance Auto Parts and likely other places like O'Reilly's. It is ATF with some seal conditioners so (warning to the turkey baster) you can just suck out the old stuff and replace it with the new. I did several iterations of that, ran the rack from lock to lock, and then sucked it out and replaced it again. It took about 1 full quart to "flush" the system.
I have not yet leaked another drop.
If you want an honest opinion try KC Autosport in Merriam. The are at more or less at I-35 and Shawnee Mission Parkway behind the pinheads at Aristocrat Motors, I think on Carter Drive.
Stay very far away from Superior Volvo, they are thieves.
If you do need to change the rack here is a link to a procedure for a right hand drive car - the left hand drive is a bit more complicated but it should help you out.http://volvospeed.com/Repair/power_steering.pdf
Always here to help out a fellow JOCOer,