I just did this repair on my other Lexus. Its quite easy; however you seem hesitant. I used to be one of those meddling boyfriends and now I am a meddling husband, so i understand your situation. My problem was that the white corrugated plastic extender/retractor was stripped inside the housing that contains the motor that moves the antenna. The part cost $44US, and took me about 0.5hrs to change. My guess is that yours will need a similar repair. I suggest that either you do it yourself, or take it to a dealer. Most Toyota dealers wont work on a Lexus, so you are likely stuck with a Lexus dealer. My guess at cost is $50us for the part, and 1hr labor (here in Canada thats about $110CDN), so about $150US.
Karl