Hi Dirk, for the resizing issue, you can use:

google.maps.event.addListener(map, 'idle', function () {
            google.maps.event.trigger(map, 'resize');
        });

this will draw the map again after the page is fully loaded.

Also you can add the click event so it will be more easy to add the content

google.maps.event.addListener(map, 'click', function (event) {
            placeMarker(event.latLng);
        });
function placeMarker(location) {

        if (marker != null) {
            marker.setMap(null);
        }

        marker = new google.maps.Marker({
            map: map,
            position: location,
            draggable: true
        });
        marker.setMap(map);

        lookupPosition(location);
        addMarkerDragEndListener();

        map.setCenter(location);
        map.panTo(location);
    }