how to fix cellar entrance that had water damage

[Joe]

My cellar entrance from my backyard has been a victim of water damage that has spanned decades. The cement has become compromised and the sides are literally crumbling. The stairs seem like they haven't been damaged so how do I go about repairing the walls on either side of this entrance? It seems like both sides of the stairs will need to be torn down and rebuilt. To add to the problem I believe I need to have the back of my house regraded because it is too level and that is probably the source of the problem. There is a cement walkway around the cellar so I suppose that needs to be removed. =Is this something I can do myself or should I get a contractor to make sure it's done correctly since there is the grading issue to contend with?

[Joe]

I guess what I'm really asking is if the water has found it's way from the outside to the inside through the cellar doorway (when it rains it streams down the side of the walls to a drain) is it even possible to "fill the cracks" and make it water tight again? I'm guessing no, since the water is already inside the wall.