I'm not sure of the config yet, but I am about to start the same basic config.
Connections:
main campus has a ds3 to our remote hospital
main campus has a ds3 to another offsite facility
remote hospital and offsite facility have a 100mb fiber connection to each other
When the ds3's to our main campus go down we plan on routing all traffic over the 20mb dsl vpn link over our ASA5520 to our ASA5540.