I have a 42" entrance door with a sill which has heaved from moisture seaping underneath , sitting on a slab. I can buy a replacement sill and try to drive it in but can't figure out how I will fasten it. Or I can pull the frame and replace it as a complete unit frame and sill. A new 42" steel door just isn't in the budget right now. Any pointers on replacing the sill versus the entire frame?