Cummins 5 year old synthetic oil with 1000 miles - change ?

Asking for a friend, (really) He has a 36 foot HR with a Cummins. He's broke and this is his primary residence. Other than switching campgrounds seasonally and pumping tanks he has no miles on the oil but he feels he needs to change it before taking a trip.

He's 75 and is in cancer treatment. $200 for an oil change is a lot of money.

Can he put 10,000 more miles on this oil?

thanks