You need to compress the springs useing some sort of spring compressor. I know fisher sells one, because we have one, and it works pretty well. Once the springs are compressed, they are very easy to remove.
Here's what I do, but it's not as safe as using the Fisher tool but much faster. I simply drop the blade against an object like the concrete lip on my garage floor and push gently with the truck till the blade trips, then with out letting the blade push the truck backwards, put it park and lock the parking brake, I get out and put pins 3/16" X 1 in the holes in the spring guides that stick up when the spring is compressed. Then I back away. The springs are party compressed and can be unbolted as a unit, the replacements from Fisher come this way. Reverse the procedure to remove the pins. Be CAREFUL if the blade is not hooked solid it can spring up, I use pliers to hold the pins when inserting or removing them in case this happens so I keep all my fingers.