You'll be able to get all dealer-service information if you sign up for the "Lexus Drivers" website with the car's VIN.
Just look at Service History after you register.

>>>Is there any harm in just replacing the front spark plugs and coil for now?

I think that's the wise thing to do. Tackle one issue at a time. Fix what you need to do to stop getting engine fault codes.
After that, you can prioritize other issues and work at your leisure.

 

Thanks! The Lexus Drivers site does have a few records I didn't get. It looks like the VVT-i line was done at 29k. Guessing that will be rubber not metal. No mention of oil cooler line.

 

Same with mine, but that's because my RX never had an oil cooler.

 

Is 12.5 - 20 ft lbs of torque good for the spark plugs? I am using a beam style torque wrench with a range of 0 to 150 ft lbs.
The '09 doesn't have an oil cooling line?

 

I think I've seen 13 ft lbs mentioned here, but I can find it when I search. For the FK20HR11 plugs, Denso cites a range of 15 -22 https://www.densoautoparts.com/spark-plug-installation

 

Some do. I'm not sure if it was part of the Towing option, or if it's a separate option on its own, but not all 2nd Gen RX's have the oil cooler.
I bought my RX used and the first thing I did was look underneath to check the status of the infamous oil cooler lines I've read so much about.
I spent 5 minutes looking because I didn't believe my RX didn't have the oil cooler -- I assumed it was standard equipment on all RX's, regardless of the tow package.