I am also new to Blender, but I can answer your #2 question somewhat about snapping the verticies together. When I got the two images overlapped closely after mirror-Y, then Used Shift S (Snap) and then Cursor to Selected to get the cursor on the target vertex. Then I selected the other close by vertex and then Shift-S and selected Selected to Cursor. The verticies snapped together! More cumbersome because I don’t know the shortcut methods, but it works.
