I walked away from a similar job last year. Low profile, ground in shiny grease, mostly full depth. No chance of a satifactery result imo. Obviously been incorrectly and insufficirntly cleaned before by someone, possibly in house, which has lead to such a soil build up.. My previous attempts at cleaneing this type of carpet with same degree of soiling, has resulted in patchy areas and the use of far too much heat and water. Personally unless the really bad area was confined to just a small part of the area to be cleaned, I would pass.
Dave.