clean Surfaces from curves

I've been running into a bunch of issues trying to create surfaces for this object in GH. When I bring in the surfaces from rhino its subdivided due to the 3d curvature of the wire frame. I'm just trying to close this up on the top and sides so I can have a clean un subdivided surface to create a grid on. I've attempted every tutorial but none really get into things this basic for what I have. 

attached is the wireframe and a section image (minus skin) so you can get an idea 

any help is appreciated.