Hi Brian: You obviously have read and understood the previous discussions on this topic. The only additional item is drilling drain holes in the bottoms of the cinderblock columns. This will ensure they drain out.
With 120 lineal feet, you may have to have more than one sump (low point) . At 1/8" to 1/4" drop per foot of lineal run, this comes out to be 15 to 30" of drop in your drain pipe.
As long as you don't dig below the footings you should have no structural issues.
Whether you install the drain in the common wall depends on if you've had any moisture problems there (or your neighbor). You might chip out a couple of inspection holes while you have your electric jack hammer and see if the sub slab dirt is moist or not. If so, I would go ahead and put the drain along that wall.
You're set. Get your tools and have at it. This is a bunch of work (a teen age boy or two would be quite helpful here) but once you have your dry basement, you will take great pleasure in knowing that the work was done right. Oh, and you'll have saved a bunch of money, too.