Question about using PC with another monitor temporarily

My sister's PC has contracted Vundo, and while I've been OK with doing some
work on it remotely (she's 6 hours away), I want to do some of the more
involved fixing with the PC in front of me (e.g. probably can't connect
remotely if in Safe Mode). I'm trying to get her to bring "the box" (and the
kb and mouse) down on Thanksgiving, leaving her monitor at home because I
have a spare in storage.

(1) Will I be able to simply plug in the spare monitor?
(2) Will she be able to simply plug in her monitor when she returns?

I can provide information about her PC and monitor, and the spare monitor,
if it makes a difference in answering the question. Thanks.