The question then is why does it get soppy? Does the soil there stay wet or does it get wet because of a drainage issue? If you build it up, where will the water run off to? I put a large bed in my back yard once only to discover that the water then had no where to run out of the yard and it pooled on my lawn. So I had to take it out. The other thing is, if you do have an area for the water to run off to, simply laying the stones around it may be enough to detour the water away from the area. 7 yrds of dirt is not that much, but I guess it depends on what your idea of "much" is. That is another reason that stripping the topsoil away (which will happen if the grass is stripped) is a bad idea, you will lose dirt that way. Every inch is precious and expensive. By layering straw over the area, over the span of 3 or 4 years your soil will be improved a lot. You may also consider having the area tilled after you spray it with round up. This will loosen the soil so it will be easier for the plants to use it.
