John:
Serviceable - that is a heavily loaded question. Effectively, these modules are not serviceable in any conventional definition of the term. They are uncomplicated devices that if used within their design parameters should outlast all of us, and possibly our children's children. The best analogy I can think of without much thought is that a Class D module is very much like a well-made Klein or Estwing hammer. Unless you abuse it, it will last forever. It will also tolerate a limited amount of abuse, but not infinite abuse.
https://www.amazon.com/Electricians-.../dp/B0002RI8VO
Buy a quality device in the first place. Build it well. Keep good clearances. Make sure the power-supply is capable. And keep it cool.
Peter Wieck
Melrose Park, PA