Well, you need to first export the frame you need by going to render and change render option to current frame. (you must have your movies already imported into a time line than you have to movie your yellow tool tip to that position), then export and do what I have written above.
Then you need to bring in that frame from what ever place you have saved it, create another group in you time line this, time Group have to be directly above your footage. Lastly place that frame above the frame you want to replace it with. Then render your movie in the same codec as your original footage.
You can cut a frame off by using the split feature, it will spilt your clip in half and then you get the frame you don't want out. Add the disolve behavior for the 1 frame blend. I think no one will notice the lose of one frame so I would not take the time to do the disolve.