Bad sensor or bad mechanics?

I hate to admit, but when you distrub systems, that tends to be when they break. I know you have run up a very high bill, and you will always second guess whether everything was needed.
If the car runs bad with the sensor connected, and ok with it not connected, I would say the sensor is probably bad. Not sure how or why the mechanic would have made the sensor go bad, but that is not really going to fix your problem. I would say have the sensor replaced, and if you dont trust the mechanic, you dont have to ever go back to them. If you feel they did something wrong to you, then let your friends know. But try and move on with the knowledge that you have done a lot of good work to your car, and it will probably pay you back in the long run by being reliable and a dependable vehicle for years.
If the mechanic told you he would replace the sensor for free, then you should have the option to go buy it from the Honda dealer and give it to him to replace. If you feel like you wont get a fair deal on the sensor. If you just want to call the dealer and see if the sensor itself can be replaced, do it. If all you need is a sensor, and it can be obtained thru a dealer, but he is trying to sell you an entire throttle body, then someone is trying to take advantage of you. Make the call to your Honda dealer parts department and ask for a price on just the sensor. If they will sell you the sensor, call your mechanic and tell him that since his supplier could only get a throttle body, you got your own sensor and will bring it to him for the free replacement. However if you do not trust this person, it may give you the best piece of mind to take your car to another mechanic and have them replace the sensor.