I don't see how the land could be sloping away from the house if the water is accumulating under it--our eyes can fool us but water won't be fooled! (BTW, I never heard of having a sump pump in a crawl space before, but it does sound like you need one in your circumstances.) Your first step has to be to determine *absolutely* that the land is sloping away from the house, because if it is, there is almost no way water could be accumulating as you describe--even a high water table would have a minimum effect if the land is properly sloped! Your best bet would be to talk to some landscaping contractors who do grading, since hopefully one of them will know how to accomplish this with minimum disruption of your property.
As for insulating under the house, that shouldn't be necessary. Heat loss is minimum through the floor, and if the floor seems too cold in the winter, this is usually because cold AIR is being drawin in to replace hot AIR leaking out through the attic! (remember, FG insulation cannot stop air flow). For more on this, I recommend perusing www.weatherization.com Some of what it says may sound radical, but it's thoroughly logical and backed up by facts.