Hi, PIZZAPIZZA. Hey, your name is fun to type! The header above is rated for the load it carries. -------- I wouldn't cut it. ---------- Because of the liability and safety issues, I would consult a Licensed Contractor or Structural Engineer. The worst - FAILS and hurts someone, the least - stress cracks in your wallboard, or door binds.
Yes, the door sits on the raised slab, with window/door wrap, or flashing, caulking, some water barrier under it. If it measures 6'10" high, new ones come stock, 6'8". I'm still reasoning why a new 4" slab - heating in floor? Is it structural? Be safe, GBR