How important is the major maintenance on a Onan generator? Is changing the oil, spark plug and filters enough

The manual says the heads need to replaced or checked every 450 hours. It is worth paying $450 for a cummins tech to look at the generator?|||It%26#039;s a gas engine they carbon up a lot%26gt; You can try running a decarbon additive%26gt; Or pull the head off%26gt;.,|||It%26#039;s a gas engine they carbon up a lot%26gt; You can try running a decarbon additive%26gt; Or pull the heads off%26gt;