You can do your own work, they cannot make you have it done at a dealer. Keep your receipts for all the oil and filter changes and any thing else you do. As said before, there is no 600 mile service. Many of us change the oil, filter and final drive fluid at 500 to 1000 miles just for piece of mind.
Magnuson-Moss warranty act states
Tie-In Sales" Provisions Generally, tie-in sales provisions are not allowed. Such a provision would require a purchaser of the warranted product to buy an item or service from a particular company to use with the warranted product in order to be eligible to receive a remedy under the warranty. The following are examples of prohibited tie-in sales provisions.
In order to keep your new Plenum Brand Vacuum Cleaner warranty in effect, you must use genuine Plenum Brand Filter Bags. Failure to have scheduled maintenance performed, at your expense, by the Great American Maintenance Company, Inc., voids this warranty.