Henry,
Welcome to Beoworld...
There are user and service manuals on the Beoworld site for all the Beolab Pentas, however you do need to sign up as a silver or gold member for access to them..
Many members have changed the foam on many types of B&O speakers and I am sure Peter will provide fully details.
With regards to the fan on the 5500, I have looked at the circuit diagram which is also on the Beoworld site and the fan is controlled by a very complex temperature sensing circuit and so the fan should only run if it reaches a defined temperature. Also as the power to the circuit is shut off when you put the Beomaster into standby means the fan will never run in standby, which is a surprise because the temperature raises most when you switch off a piece of electronics equipment.