My experience with the Toyota maintenance plan is that it's a complete rip off. My parents got it on their Toyota. I didn't. I go to Firestone and can get oil changes for $20, replace my own filters for $10 from Amazon, etc.
Lexus may cost more to maintain but I doubt it that's much more. I'd ask for a refund.
The warranty is a little trickier. It's a rip off but its also peace of mind. Most experienced car buyers don't get it. Again, its a Toyota/Lexus so you don't really need it.