If you are able to access the Time Capsule using AirPort Utility, you can rename the Time Capsule as follows:
Open Macintosh HD > Applications > Utilities > AirPort Utility 6.0
Click on the Time Capsule icon
Click the Base Station tab at the top of the window
Edit the Base Station Name as you wish
Enter the Base Station password...(.if you want to change it)
Click Update at the lower right and the Time Capsule will restart in 25-30 seconds with your new settings.
If you want to change the Wireless Network name and/or password, click the Wireless tab before you click Update and make the changes that you need.