It may work, however you should setup either an out of band connection
(dialup to that network) or possibly something like a sonicwall 170 that you
could give an external IP to and VPN into that network to work on the ISA
from the private side of the network in the event your external connnection
was unaccessable. However it sounds like you don't have that ability to get
something like that setup prior to your change.
MCP, MCSA, MCSE+Security, CEH, CCA