You don't actually remove the u-joint itself.
What you have is a u-joint assembly.
You unbolt the assembly on the steering wheel shaft on the top side and the steering rack shaft on the bottom side.
Once they are both loose enough, you slide the u-joint assembly up or down to free on side and then slide it off the other way.
That's how it works on the 2002/3 model.
I presume it works the same way on all other models as well unless, in their infinite wisdom, Subaru decided to change it for absolutely no reason except to cost you more money