TBH I wouldn't run such a campaign with AToW, because while it's a decent RPG for running a SciFi military-themed campaign, the heavy crunch of the rules would get in the way of a survival horror setting like Resident Evil. If I were to run a RE campaign, I'd use Savage Worlds Deluxe with the Horror Companion. The cores rules for it are much simpler with more fluid combat, while its Horror Companion supplemental book has good content and details on how to run survival horror (that book calls it Action Horror) campaigns. Not to mentions it's cheap and you can get both of those books for around $30; less if you're cool with PDFs. There's also an existing 3rd party setting for SWD called War of the Dead, which would give have a lot of the monsters, NPCs and adventures.
Another system that's good for this sort of horror campaign is the Basic Role Play system. It's been a while since I played in or ran any campaigns with it, but it's popular for horror settings and works well for them.
Of course if you players are very familiar with AToW, then that would help make it a more viable option.