as someone said here an server update can take more then 2-3 hours , you realy need to change your host (i cant believe that you are ok with this -2-3 days down).
Knowing that you are based in US i starting to think the worst ........i think your data center lie you.Yesterday they say you will be back in a few hours.They are even tottaly incompetent , or you will be shutting down by them.How they can tell you 2-3 days for upgrade a server"??