1.
The best way to copy a layer from one file to another is the following:
Select the layer you want to copy and rightclick.
Select Copy layer
Then in the windows that opens select the target of the layer, eighter another open file or a new to be created file.
You can also drag and drop, but this way ensures that the layer is aligned exactly the same way as in the original image. That is, when the images have the same size.
Here is some more about layers:
http://www.simmerspaintshop.com/foru...photoshop.html
2:
Selecting new colors you do in your toolbar. Doubleclick in the foreground (yellow in the example) or background color (brownish in the example)
To replace an existing color there are many ways.
When the layer has an equal color this way comes closest to what you are used to do:
http://www.simmerspaintshop.com/foru...ing-color.html
Here is another way:
http://www.simmerspaintshop.com/foru...ng-colors.html
And here is a way for complex situations where multiple colors with gradients/anti alias are involved:
http://www.simmerspaintshop.com/foru...one-layer.html