Lexus Troubleshooting Questions? Ask a Lexus Expert
What happened to it or why are you trying to repair it? Any pictures?
Can you recheck the model or the year? There is no IS 250 in 1999. Do you have the VIN available?
If you're getting oil leaking from and behind that gear it is not the gear that is failed it is the seal the bad news is in order to remove that seal you have to remove the camshaft assembly than the gear is disassembled from the end of the cam in order to get to that seal to replace it. Click this link and download the illustration. Please not forget to rate the assistance that I provided you at three or higher.
Try this link they other did not work for some reason. Save the illustration it will time out.
Did you get this resolved?