Swapping out non working speedo/adding a radio

going to be swapping out a non working speedo with a used unit on a 1968 Dart.

Question 1) my gauges other than the speedo work and the used one has gauges with it as well i'd like to just do the speedo swap is this as straight forward as it looks to be (remove the speedo back plate and mount screws).
2) Other than dropping the steering column to get the room to remove/install the cluster and disconnect the battery is there anything else that i should be prepared to do.
3)adding a radio and speaker to a radio delete car using a 68 radio and retrosound dash speaker anyone have any experience with retrosound is it a straight bolt in with regard to the speaker and would the wiring harness have the power/ground wires stubbed at the radio junction or do i have to run my own. Last i have ham hocks for hands should i remove the heater controls to get some room or is there room enough to work there.
Thanks Jim :poke: