I'm not sure what's in the link but I expect it includes a reference to a Snap-On tool. In my case, I was able to remove the rear upper bolt by removing the dipstick (13mm head bolt through the intake manifold into the head, then pull it out, watch for the 0-ring), removing the bolts that hold down that thing on the intake manifold held down by two 10mm head bolts (don't know the name off the top of my head) then going at it with a 1/4" drive 13mm socket with u-joint and 6" extension (Craftsman, in my case). The rear lower bolt is easy enough with a 9-12" extension.

I found it easier to fit the allen head bolt from the front upper location in the rear upper location. A 6-8" 6mm hex key with a wobble tip does it for me.

I put the rear upper bolt in place with the help of a parts-picker-upper-magnet-on-a-stick.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD