I would say it is a bit more than 30 minutes, closer to an hour or two based on your skill level. For me, the most difficult part of the dash removal is removing the heater panel and it's associated cables, the radio, and the wires that go to the fuse box. It is probably easiest to remove the fuse box along with the dash harness instead of unscrewing the two wires that attach to the bottom of the box. The rest of the removal is easy by comparison in my opinion.
Also, you will want to take a lot of pics of the smaller individual wire connections. There are several that change color and this can be a bit tricky when re-installing. The larger connections are basic.
Also, I would recommend 'Just Dashes' over purchasing an uncracked or NOS dash. There is no telling the condition of an old dash and how old the plastic is and what it has been exposed to.
Just my thoughts.