I need to combine two images into a single image and then I need to add a swirl that splits the two images but I want to blend the swirl with the two images. I don't want it to look like I just added a swirl on top of the two images. How do I do this? Is Photoshop the best program to use?
Two layers, one photo in each, same layer mask for both, but the other is inverted. Can be as wild as you like.
You can add the complexity by filtering the transition zones by a complex geometric distortion filter.
ADDENDUM: Try a simple gradient at first. Then smudge aroud a little the transition zone. You can smudge also the masks. Do it differently in both layers => you can add a third (=background) layer that increases the complexity by having some texture.
If you are good to judge what you want and have the ability stop before it's too late, you do not need the masks at all. Erase from the top photo what you do not want to show at all. Then change the eraser to soft bush and 25% opacity and create a soft transition. By using smudge you can add geometric twists. An occasional small overdo can be covered by undo or by cloning.
The following is a zero artistic value technical example of this no-mask method.