Most power supplies have a fuse inside them on the board, although I have never cracked the one in my 4000 open. I'd say it's worth a look inside. If you get off that easy I don't think I would try again without looking in to the monitor/FF/Amiga pinouts a little closer.
I plugged an older working 19 inch monitor in to a PC years ago and blew a trace on the graphics card. Since it was a PC I just tossed the card and never tried that combo again, but your 4000 must be saved! :-o
Good Luck.
