Yes it's very doable. I do that pretty often to create fake HDR from the same photo at two different exposures. There are many ways to achieve this, it depends on how proficient you are with the selection tools and layer masks. I'm confident you can do it.
First, put your two photos in the same file, on different layers and create a layer mask in the top one. Without the layer mask, the top layer would completely hide the bottom layer. The bottom layer will be made visible "through" the mask by painting in the mask itself. To simplify a bit: anything that is black/grayscale in the mask acts as a "hole" through which you can see the bottom layer(s). If you are not familiar with masks, start with a black or white brush and experiment to get a feeling for it, it's fun. Now if your darkest photo is in the top layer, paint in its layer mask to bring back the corresponding regions of the lighter, bottom layer. Congratulations, you now have a composite of both layers.
Now there are two points to keep in mind, in my opinion:
1) How do you select the dark and bright regions to create your mask? I would recommend you go to "Select -> Color Range" and either: a) use the "Sampled Colors" mode and Fuzziness slider then just click (and shift+click) in the dark or bright regions of your photo to create/expand a selection, or b) use the "Highlights" or "Shadows" mode to directly select bright/dark regions (to some extent). Once you click OK, select the layer mask and use "Edit -> Fill" to fill the current selection with black (invert the selection before if needed using "Select -> Inverse").
2) How do you handle the transitions between the darker regions of your top layer and the brighter regions of your bottom layer. This is the tricky part. My way to do it is to apply a "Filter -> Blur -> Gaussian Blur" on the mask itself. Since black is fully "see-through" in the mask and white is opaque, a Gaussian blur will create a smooth grayscale transition in between these 2 areas, thus blending both layers somehow. Make sure to enable the filter's "Preview Mode" so that you don't overdo it and create unsightly halos. The layer mask is basically a grayscale picture, so most of the paint tools or filters you are familiar with will work there. For example, I use selection tools to Gaussian blur some part of the mask more than others (say, trees vs. sharp transitions).