The way to take a fingerboard off is heat and slow careful work with a good tool.
A good strong putty knife might work well.
I've used a clothing iron resting on the first couple frets, let it sit for a bit to warm up the area.
Start at the bridge end of the neck, and very carefully get the thinnest strongest metal device you have
to help get between the fingerboard and the neck to release the glues. An exacto, knife or screwdriver can also work
to get things started.
Don't pry upward if at all possible. Also it's best to not try and get too much at a time. I usually would get in about a fret, and
then go all the way across to the other side, then go deeper and work your way along.
Slowly carefully and methodically work your way down the neck.
The first one I did was a completely nerve racking experience, it gets more comfortable with time and experience.
Also depending on glues used, it can go from easy to very challenging, every instrument is different.
If this seems too scary, have a pro do it. Otherwise if you're adventurous and have some wood working skills, it's a great way
to get into repair work for yourself and others.
I'm sure there are plenty of YouTubes floating around that show, at leas on guitar, the same goes for basses.
Best of success to you.