If you have all the tools, and everything goes just right, and the new box has the bracket & Pitman arm already attached ... I'd say you could do the R&R in 2 or 3 hours. But not if you follow the procedure in the book !
The trick is that the later split column box will come out through the engine compartment, so no need to pull the front apron. You'll still need to pull the stator tube & wires out of the column; and the engine will need to be taken loose and jacked up; but it can be done. ISTR I took the LH horn out too.
When reassembling, be sure to leave all the bolts loose (including where the bracket clamps to the box) until the column is connected and lined up.