The best help we can give you is to MAKE SURE you need the sensor (s). Second is that if you don't already have the sensor, BUY ONLY original eq. Denso. It's really hit and miss otherwise. I've been down that road and wouldn't ever buy aftermarket (or universal) again. I simply wasted the money.
You can find the OE online for a lot less than the dealer. You can even buy online from Lexus OR Toyota dealer for a lot less than at the walk-in dealer.

 

I'm replacing the rear (post-cat.) O2 sensor on my 1999 ES300 and the wire appears to go into the frame under the driver's seat area. I suspect the plug is under the carpet, but does anyone know how to get to it...easily? I can't believe they'd bury a plug like that; had an SC300 and everything was easy to find.

 

The manual says to remove the seat, hopefully that is not necessary.