If I have a screen that looks like this.
and I eventually end up with a screen that looks like this.
How can I get back to the screen first shown above with out starting all over?
Thanks
You can easily save your screen layout which allows you to quickly change between the original and your custom layout - see this answer here:
You can also simply drag the small right triangle at the bottom of the left hand corner of your dope sheet down. Then drag the left hand corner of the 3D view panel down to replace the timeline panel. Once, that is done just pull the corner of the 3D view panel to the right.
Hope this helped.