Just did mine. A couple hints:

Remove the bolts from the subframe mount first so you can swing the control arm around to hit it downward with a heavy hammer to remove the spindle.
Pry open the spindle clamp a little with a cold chisel and hammer.
Use PB Blaster on the spindle/clamp when removing.
Be sure clamp bolt is completely out. Hit the arm downward HARD, near the spindle to remove it.

You may need to carefully tap the new spindle completely up into the clamp. Be sure the spindle is completely inserted so that the bolt shaft keeps it from falling out, before tightening it.

Before tightening the new arm at the subframe, jack up the suspension while the car is still on the jacks to bring the level to that of where it would be if the wheel was on the car and full weight applied. This may be an easier method for you than trying to torque the subframe bolts while the car is on the ground.