A month for an oil change? Was it a warranty job (no cash from customer so no hurry for the service)? Is there not a oil drain plug under the gearbox?
I haven’t owned a bike for 20-odd years but back then I did all my own minor maintenance (oil, plugs, tune-up, etc) - wasn’t hard. But as I said that was decades ago ...
They had to order a part (tail light). Thay delayed service until the part came in. They had me by the base of my snardleys.
https://www.youtube.com/watch?v=Z9ejIk7c6Sw