I did this with (2 screens on) FS2002 a couple of years ago. Off memory it
was a little triky to resize the views and place them where I wanted them,
but the biggest issue (at the time) was the hit on performance - 25 fps on
one screen -v- around 5 fps with 2 monitors going - although obviously
things have improved a lot since then.

Food for thought - many video cards these days have 2 outputs - the usual 15
pin mini-din and another (digital?) output - which you can convert to a 2nd
15 pin mini-din with a cheap adaptor (we do this all the time). For a 3rd
monitor consider using any old PCI based card and use it just for the
instruments?