From a previous post request.

The compressor replacement is pretty straightforward. This is for my 1993 940. I have bought used compressors for $60, and new ones for $250. A drier will cost you about $50. Misc parts, around $25. Total driveway wrench time about 2 -3 hours. Depending upon your skill and the value of your time, you might be better off with a shop. I was quoted $700 for a compressor replacement too. In the end, I ended up spending that much to replace my compressor 3 times, evaporator, drier, and 2 pipes, + VOV. All of that work would have cost me over $3000 at the dealer. However, some of the work was self inflicted because of my inexperience with A/C systems and ham-fisted approach, so keep that in mind when you try to determine the real cost of DIY. Here's the procedure from the tech manual with a few of my own comments.

1. Drain and recover the system - Disconnect the battery
2. Remove the air intake pipe and hose for better access
3. Loosen bolts on compressor, slacken adjusting bolt, remove belt. May have to do same for alternator if you need access.
4. Disconnect power supply and ground to compressor
5, Disconnect hoses. The small one is 22mm. Plug the hoses.
6. Remove compressor from engine. These are actually the bolts going thru the brackets. I found this easiest from underneath. I had the car on ramps to make it easier. You'll also need to remove the splash shield. There is also a hose clamp that needs to be removed.
7. With the compressor off the engine, remove and re-use the brackets. Pay attention to the orientation and be sure to reattach the hose clamp.
8. If you have a new compressor, drain the oil out by tilting and rotating the compressor. Do this anyway even with a salvage yard compressor. Measure the amount of oil coming out and replace with the same amount of oil for your freon type. The compressor should contain at least 50 ml of oil. Some compressors take 70 ml. Some as much as 240 ml, depending on make. Do not overfill, or underfill. Try to get the manufacturer's stated capacity. Also, don't believe the parts guy that it comes pre-filled with oil if it's new. Well, it does, but that is shipping oil and your new compressor will seize in a short period of time if you do not replace it with the proper oil for your R12/R134a system. Ask me how I know! If you don't you may get the opportunity to do this again. Do it anyway. Oil is cheap, compressors are not. Has to be done with the compressor off the engine. Look for a drain plug on the compressor. You'll need to tilt and rotate to get it all out.
9. Reattach compressor and all connections, including hose clamp. Reattach hoses with new o-rings. It is important to use new and proper o-rings. Black or blue is for r12. Yellow is for r12 and r134a. Torques (ftlbs)
compressor lp line 29.5
compressor hp line 18.5
10. Replace the drier. Fcpgroton will not honor the new compressor warranty without replacing the drier. Besides, it's probably shot if your system has been opened for any amount of time. Be sure to use 2 wrenches and be gentle. The evaporator pipe connections are very fragile, and you would not have to replace that. Believe me! See my other how-to for proof.
11. Might as well replace the oriface. I used the variable type. Pay attention to the orientation. Important!
12. Put everything else back together
13. At this point, I take it to my mechanic for getting the system vaccummed and refilled.

Hope this helps. Good luck,