You can save a bundle by doing the installation yourself. All you need
is to uncover enough of the line coming from the well to insert a T.

In addition to what Michael said:

If the tank is where it is subject to freezing, you will need to add a
shut-off valve (use 1/4 turn ball valve) and a method of draining the
tank. .

You really don't need another tank (assuming you already have one)
unless you are after more storeage. Just a frost-free standpipe at the
well or other convenient spot along the line to the house.

If you do install a tank you will need to pre-charge it with air before
it fills with water. Proper pressure is 2psi below the cut-in pressure
of the pressure switch.

Harry K