Your between a rock and a hard place here ;-{
If you can't see the drive and the Ethernet/WiFi ports are working you'll need to take the HD out and drive connecting it via USB or FireWire port of your mac system.
At this point the you could try running Disk Utilities but any data on the drive will be lost as the format of the drive is unique to the Time Capsule. You should be able to format the disk for Mac OS and test it. More likely the drive is gone.