Service on a used dump truck?

I went to the auction and bought the 1994 Ford L9000 with the Cummins M11 I was looking at. The check engine light is on but the truck runs great. It could be as simple as the coolant is a little low. I'll take some anti-freeze when I pick it up. Anyway I'm going to take it to a service shop to have it checked out and get a print out of all the engine info and see if any codes come up. I'm going to get them to do a basic inspection to make sure there's no glaring problems. I'm thinking I should get them to do a service on it for piece of mind. They said the service could be $500-$700 depending. The truck won't get used a lot as I'll just use it on my land. According to writing on the filters I think it has a little less than 300 hours since the filters were changed. Do you think it's worth getting a complete service and sending an oil sample out on the old oil? The shop charges $170/hr if you're wondering but I'm thinking while it's there just get them to service it inside their shop and I'll be good for a long time. It would be a pain for me to do it outside since it's pretty wet and muddy at my land right now but I want to use the truck in a couple weeks.

Service on a used dump truck?