how simple is it to change a "field"

on a form?
OK, user registration, then later user admin area, the location field.
Now it's filled via a drop-down list. We want that to be a text field where they can write in their location, like Des Moines, Iowa or Springfield, Missouri, or Toronto, Canada or in the case of our Aussie friends, their location like WA, Australia and so on.

The country is too limiting, especially if say the forum was used by people who were almost all in the states anyway. Or perhaps other regional forum uses - then all members would be in the same country.

so, we want to change from the drop-down list to an open text field so they can simply type a location.

I've added the 50 U.S. states to the drop-down, then a fellow from Quebec, Canada nicely pointed out.................