Why on earth would you want to change from a kind of pump that lasted 34 years to a kind of pump that won’t last a year? The following link has dozens of posts from people who have had major problems with that type of pump. You are switching from a 3450 rpm pump with no electronics to a 10,600 rpm pump that has a computer built in it. How important is it for you that water actually comes out of a faucet when you open it?
The buildup in the pipe sounds like iron bacteria. After the pipe dries, stand it up and hit it with a hammer. All the dry red stuff will fall off. Then switch the pipe on top to the bottom when setting the new pump. Chlorine shock usually helps with iron bacteria. And don’t put an extra check valve anywhere. The one on the pump is all you need.