"On the
Gubeikou map, it's near where it says "Jing Cheng road"."
So, esentially, according to the map, drive through the tunnel on JingCheng Highway, take the first right, go right again up a hill, when you hit the wall, follow the path to the less dangerous approach, and then take to the wall. Is that correct.
I have a suggestions. In the future, map directions, such as North, South, East, West, would be helpful. Although it is generally understood that GBK (GuBeiKou) is north and west of SMT (SiMaTai).
I did this hike 10 years ago and we approached via a remote village, not via GBK town, so I'm a bit fuzzy on details.