If you are thinking of changing the Cabin/Pollen filter here is a mini guide on how to do it.
Remember to put the a/c system into "recirculate" mode before you start. If you have done this the lid over the filter will be up when you remove the cover at the back of the glovebox.
On no account try to force up the cover to get at the filter ... you will damage the selector levers and it is either very time consuming and fiddly to repair, or will cost ££££'s at Lexus.
If its not up...turn the ignition 'ON' and select recirculate ... you should see the cover lid lift up to reveal the filter.
10 - 20 minute job. Fiddliest bit is removing the shelf bits in the glovebox compartment.
The picture should make it all clear.