You want the entire left-frame gone in cPanel AND WHM? In WHM, that's like the entire functionality. In cPanel, it's great information. I highly suggest you *don't* do it.
You'd be able to reskin it to have transparent gradients, but you'd have to edit the coding of cPanel in order for it to NOT display the information in cPanel. In WHM, you might be able to just remove the IFrame in the coding and it'd be done.
I HIGHLY suggest you don't do this, as cPanel might not like it. I'd consult with one of their representatives before doing anything like that.
Hope that helps!