What would you need to check for in the computer to maintain the standard monitor and to add an additional medical grade high resolution monitor?
You will either need a "dual-head" video card, or two video
cards. Check that the medical monitor conforms to a PC standard -
it may not. If it has a HD-15 or DVI video connector, then it
should be standard - and easy to find a card that will work with
it. If it has 3,4, or 5 BNC cables for video it will be much
harder. In that case you need to look for a workstation graphics
card - and probably something that is obsolete now. (Cheer up -
that means it's cheaper!)
To use the full capabilities of this "high resolution" monitor,
you may need to use a workstation graphics card even if the monitor
has a standard connector. Check the refresh rate and resolution,
and then compare with high-end consumer cards, and with workstation
cards.
Some cards will support a very high refresh rate, but only at
low resolution.
By "workstation card" I mean something like an nVidia Quadro or
3DLabs Wildcat or ATI FireGL. Note that these can cost upwards of
$3000.