I will answer based on my background as an electrcal engineer since the sensor and at least part of the autofucus system are electronics.

Pure water, as a general rule, is not harmful to most types of electronics. However if the water has any impurities in it, it can cause corrosion which is harmful. It doesn't take much in the way of dust, minerals, fungus etc. to make water corrosive. The general rule for electronic devices that have gotten wet, is to rinse them with distilled water and dry them with gentle heat such as a hair dryer on low or by placing an incandesant light bulb near by. I would NOT recommend rinsing your lenses or camera sensor. Introducing that much water would likely cause more harm than good.

The sensor is made of silicon which is okay with water, but all the tiny metal connections around it and in the other electronics of the camera and lenses are subject to corrosion. The good news is that water vapor is usually relatively pure water. Condensation is more of a concern because it will pick up dust and move it arround. The presense of liquid water can cause malfuctions, but if it is dried up without corrosion, normal function is likely to return.

For your lenses, gentle heat is the best you can do short of sending it to the manufacturer to be disassembled and cleaned. Don't overdo the heat.

For your sensor, if you can see condesation on it (I am assuming a DSLR where you can see it) I would do the incandesant bulb thing to dry it. I would not blow warm air into the body of your camera, as you would likely stir up too much dust. If taking a picture of an all white or gray background does not indicate spots on the sensor, I would not clean it. If all your photos have spots in the same place, have it cleaned, or clean it youself using standard practices for cleaning dust spots. There is plenty of info on the net on sensor cleaning.

Higher end lenses and cameras have seals to keep dust and moisture out and a water tight enclosure would also, but is not very practical in many situations. Do what you can to keep dust and moisture way from your gear and wipe it off if you can't. Condensation can be minimized by making temperature changes for your gear as slow as possible. Hope that helps.