Removing sideways installed frets is not difficult if you are courageous and have good hands. Use a steel point and hammer to make a dimple in the crown of the fret near the end that went in last. Then angle the tool to move the fret out of the slot a quarter of an inch or so. Then grab it with a pair of pliers and pull. The fret will slide out like a drawer.
A steel point can be made by grinding an old nail set to a sharp narrow point. The size used to set finish brads is best but any hard steel rod will do.
This is not a job for the casual tool user. It is very easy to slip off the fret with steel point and make a large hole or plow a huge trough in the fingerboard. If you are not handy in the extreme, please allow a professional to perform this task.
Primum non nocere.