Holy Crap! I would take it on as T&M with a possible completion date of whatever fits in your schedule. that is DAYS of work. sounds like nothing is working anyway so they arent missing anything if you take it down...

Leave the network in tact and cable distribution.

Make the deposit a weeks worth of labor and then use an equipment retainer. Midway through the week you should be able to give them an estimate of what it will take to get it back up and running.