You are in for a very major repair if the pin comes out and the slide rail falls down and gets caught in the crank sprocket! With the pin out like that there is only a tiny bit of the pin holding things together.
The pin does not screw into anything. It is driven into the block, through the slide rail, and into a hole on the other side or the rail. It is sort of a "press fit."
The outer end of the pin has a threaded hole, which you can see in one of the pictures. The impact puller/installer has a male threaded end which screws into the pin and then you user "hammer" part of the puller/installer to drive it in to the block.
You can use a hammer and a drift pin to drive it in, but don't damage the threads.
This is the only picture of the tool I could find.
Hope this helps
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe