Gasmanmark

hi im mark from epsom , surrey 2 years ago i bought a grand voyager 2002 crd 2.5 diesel with a disability ramp fitted (i have a great dane who cant jump too high so it helps her get in) its been great , but lately theres a real noticeable loud tapping sound from the engine ,ive looked at all the receipts but theres no sign of a timing belt that's been changed, ive decided I wont drive it until I know whats wrong ,Is it possible for an average diyer to change the belt as I would prefer to if I could , thanks mark