I know this may seem like a simple thing , unless you have never done it before. Here are a couple of pictures and descriptions to give you an idea of what is in there.
The blades I used are Woods 3975 KT on a Woods 42 so common on the Cubs on this area. Here is a new blade compared to a worn and bent one.
The blade mounting assembly is acessed here.
As you can see there is a mounting bolt with a 3/4" head over a washer with a half circle cut out of it.
Loosen the bolt a bit and revolve the washer until it exposes the top of a round cylinder . (The cylinder will be closer to the arbor)
The cylinders are visible from below protruding below the mounting iron.
Reach under the mount and push up on the cylinder until you can remove it.
The blade is now free to remove by sliding it out of the mount which should move fairly freely.
Reinstall the blades using reverse procedure and you are home free.
Check the condition of the cylinders and all components and replace if necessary.
If you are replacing a damaged blade you should replace both of them if using new blades. The unbalanced weight of the blades will cause additional wear to your bearings and eventual failure.
I hope this helps someone