This is an easy job if the pump handle nut is not too tight. I would suggest getting the wrench for this. I see them all the time on ebay for cheap.
If that pump handle nut is tight, take your time and use some penetrating lubricants. If you twist on it too much, you can tweak the slide rails. Ask me how I know this!
You can straighten them but it takes a long time. Ask me how I know this as well!
The advice on the screws is good. Use a large phillips. There should be small holes in the butt pad that look too small to push the driver through. It will go through. Use a drop of oil if you must. I spun the heads out of one of mine and wound up drilling a big hole through the middle of the pad so I could insert a long flat head screwdriver. I unscrewed the stock bolt with the boogered-up pad still in place, the brail (sp?) method.
I still have that butt stock hanging around with the ragged recoil pad still on it.