I forget the exact price for the draft arms, but around $250 as a dealer-installed option sounds to be in the ballpark. One trick to that - I've heard from other people that they've bought them afterwards for the same price quoted for the up-front option cost. But in that case - by just buying them as 'parts' now you've got both sets in case you ever need them, I've only got the extendable ones. Worth investigating the pricing with your dealer.
My tractor's 50 miles away from me at the moment, so off the top of my head, I would say the links extend about 2 inches, and have a vertical movement of about +/- an inch.
In other words - they don't move drastically - but they usually have enough flexibility to be able to hook up, even if you've only backed up 'close' to correct. I usually try to make sure the draft arm eyes far edge are just about even with the front edge of the implement pins, front-to-rear, and slightly lower. At that point, the arm ends and the hitch itself has plenty of movement in all 3 axis to hook up without getting out the old armstrong bar to lever the implement that last 1/2 or 1 inch.