You don't actually even have to visit google earth to get the coordinates. If you want to do it using maemo mapper you can just zoom out until the displayed map is surrounding the area you want to download and maemo-mapper will already have selected the area for you. You just just select Maps, Manage Maps, click on the zoom tab and select which zoom levels you want to download.
Or you can download along routes, if you look in the documentation, so you don't have to download a whole square of maps (a lot of which you might not want)