This is what I did for my 2006 Legacy GT, other years may be different.
So recently (like a number of us out there) I looked under my car an found that I had torn one of my CV boots, specifically the front passenger one.
http://farm4.static.flickr.com/3642/3393868684_d79d9b2f16.jpg?v=0
Ewwwww
http://farm4.static.flickr.com/3539/3393868502_32a55ceeb0.jpg?v=0
So Like a good subaru owner I decided to fix it myself.
Now in my case I actually rebuilt the cv joint, most people would recommend just replacing the whole thing. After doing this job, I might be inclined to agree. However, doing it myself cost me about 40 dollars (parts and Axle nut socket) versus $340 for an OEM one.
If you do the whole rebuild and have never done one before, it took me 3-4 hours, if I was just doing the axle, it would have been about 20-30 minutes.
Here was my Tool List:
Breaker Bar, long one.
32mm Socket to break the axle nut
14 MM Socket
14mm Wrench
Allen key set for swaybar
BFH
Rubber Mallet
Snap Ring Pliers
needle nose pliers
2 flathead screwdrivers (small)
2 Cans of brake/engine degreaser/cleaner
Gloves
Lots of paper towels
Parts:
New boot and greese kit from local Subaru Dealership.
New strap for cv boot from Checkers, since one of mine broke, you can try reusing the ones you have on there though.
I used these directions in this thread as reference, but things were slightly different, close but not quite- http://forums.nasioc.com/forums/showthread.php?t=1393149&highlight=axle+replacement
First Raise the car and I put a jack stand under the passenger front side of the car, took off the rim and tire and went to town
Unstake the axle nut (you will see it is crimped) I used a screwdriver and my BFH) Killed two screwdrivers
Then since I have an aircompressor, fired up the impact wrench and took off the axle nut. Since it is supposed to be torqued down to 137 foot pounds, I set the compressor at 150 and my gun to max.
http://farm4.static.flickr.com/3622/3393058887_7e8bc16344.jpg?v=0
Next I removed the bottom swaybar bolt with my 14 MM socket (it went back on differently, use the allen key and a 14 mm open or ratcheting wrench if you need too)
http://farm4.static.flickr.com/3449/3393869516_581a718679.jpg?v=0
I had to jack up the bottom so the bolt would pop out
http://farm4.static.flickr.com/3555/3393870744_8d8d700e21.jpg?v=0
Then I took off the lower ball joint retaining nut, looking at directions online without pictures, finding this thing was a real AH-HA moment.
I believe this was also 14mm, but may have been 17mm.
http://farm4.static.flickr.com/3467/3393059693_22791b8810.jpg?v=0
I was then able to take my prybar and just pop out the balljoint, this was really pretty easy.
http://farm4.static.flickr.com/3564/3393871468_1e260cd336.jpg?v=1238288582