the list can get mighty if your even a bit paranoid.
The first thing I would check is the date code on the tires. (not just pressure) tires age out before they wear out on most RV's depending on the size of the tire and the weight they are carrying the sooner they need replacing. 7 to 10 years is the excepted replacement age.
I am going to guess that this is a Motorhome and not a farm tractor towing a trailer.
Next to check is the hoses on the engine (of course you would want to do that on the tractor too) don't forget to check the heater hoses as well. If they let go the engine will overheat as fast as loosing the Rad hose.
next would be brakes and brake lines just to make sure you can get stopped.
I personally don't change the oil in the first few hundred miles of having a new to me vehicle
This list would be regardless of what kind of motorized transport you are planning a trip in.
John Deere was an RV chassis manufacturer for a short while. Their RV chassis business was sold to Oshkosh, which itself was later sold to Freightliner to become the Freightliner Custom Chassis Corp. that we know today. To the best of my knowledge, John Deeer never actually produced a motorhome - just the chassis. It used a Ford gas engine, usually the 460. Several RV manufacturers built coaches on the John Deere chassis, including Fleetwood, Gulfstream, Winnebago and the now-defunct Hawkins. Probably others too.
Gary, thanks for that clarification. When I saw the subject I wondered because I never heard of John Deere building RVs. So the next question for the poster is, what is the name of the RV you are buying?
Oh and pictures (seeing as you are picking it up today) we need pictures you MUST take pictures and then post them here for us to see. yep that will make your rig work better
Dutch Coach-net has a short waiting period does it not? ( I admit I have not looked into that yet) I know the CAA/AAA has a waiting period of 3 days so you don't just have them tow a junker home for you.
The OP here has not given us a lot of time to help. So I hope she will have a safe trip home and then come back and ask many questions we can help with after.