inorder to not void the warranty, just save all your receipts and invoices.
There are a few pages that discuss this in the owners manual.
For example, oil changes, tire rotations, tranny flushes, etc. don't always have to be done by a Lexus dealership to keep the warranty intact. These manit. procesdures can be done by oneself, a Toyota Dealership, Jiffy Lube, Sears Automotive or an independent shop of your choice.
steviej