I'm assuming you have a 4-cylinder, right? I wondered the same thing when I changed my diff fluid last weekend. I had to raise the car up to remove the drain plug, but when I went to add the new fluid, I put the drain plug back in and lowered the car. I went ahead and removed the plastic intake tube that runs from the throttle body so I could have more room from above. I then went ahead and was able (with gloves on) to reach down and remove the fill plug, insert a long hose and fill up the housing that way. I put a little container under the differential so that when it filled up, I wouldn't make that big of a mess. Then, all I had to do was remove the hose, put the plug back in, and reinstall the intake hose.