The export tab in phpMyAdmin only lists databases, so you need only select the database.
To make changes you'd either need to script them yourself using "alter table" statements, or manually edit them in phpMyAdmin. I find it easier to manually edit. It's probably safer when you're doing it on a test system first, then on a production to script it. But I'm not a database wizard, so it's just way easier to adjust the column properties on the screen.
I, too, depend heavily on community support, so I try to give it when I can.