Any problems with 3.0 V6 Mercedes engine on Class B Van

HB's on some modern engines are considered wear items these days. They are part of the maint. schedule and IF inspected at the required interval, will pose no problem at all. This is because they don't "go out" all at once. They sometimes slip a little and this is caught at inspection time before it's a real issue.
That would not keep me from buying that engine anymore than it would keep me from buying a Cummins engine - which has the same inspection requirements.