Inherited a John Deere 4120 -- Self Maintenance or Dealer Service?

Hey everyone,

I recently inherited a John Deere 4120 PowrReverser Tractor, and it's a beauty with just 390 hours on it. It’s about to hit the 400-hour mark, which (if I understand correctly) means it’s due for some scheduled maintenance.

I called my local John Deere dealer to get a quote for them to come out and service it. They quoted $560–$580, which includes parts, but they also added the usual disclaimers about potential extra costs if they find issues.

Here’s the thing: the tractor runs like a dream. It was owned by a master mechanic who kept it in perfect condition, and I want to continue that tradition. But when I looked around online, I found the John Deere 4120 Engine Maintenance Kit here for about a third of the price.

So, I’m wondering:

1. Is it worth doing the service myself to save some cash, or should I let John Deere handle it for peace of mind?
2. Does the hydraulic fluid (or anything else) need to be changed, or is it more about just topping off fluids?
3. Any tips or advice for someone new to maintaining a tractor?

I want to make sure I do right by this machine, but I also don’t want to throw money away unnecessarily. What would you guys do?

Thanks in advance!