Use exactly what is recommended by Lexus as listed in your owners manual.
On the 2008, the manual says 5W30. However, many Lexus dealers use 5W20. I assume this is to try and improve gas mileage slightly.
there is an small key inside the key less remote that comes out, use that to get in.
Lexus uses Toyota oil filters for their vehicles, so yes, you can use Toyota oil filters for your Lexus.
The 2013 Lexus IS-350 runs on premium unleaded (required).
The 2013 Lexus IS-250 runs on premium unleaded (required).
The 2013 Lexus IS-F runs on premium unleaded (required).
The 2013 Lexus ES-300H runs on regular unleaded.
The 2013 Lexus ES-350 runs on regular unleaded.
The 2013 Lexus RX-350 runs on regular unleaded.
The 2013 Lexus CT-200H runs on regular unleaded.
The 2013 Lexus GS-450H runs on premium unleaded (required).