You aren't supposed to touch the interior of the lens the same way that you're not supposed to touch the bottom side of a CD/DVD.
Just be gentle if you ever have to wipe away any dust or smudges because the anti-fog coating is thin. If there is dust then use a microfiber cloth (like the dust bag the goggles come with) to wipe it away, or you can blow it off with your breath.
What do you mean by moisture inside? If moisture gets inside the goggles (between your face and the interior of the lens), then it is best to get some airflow going that will make the moisture evaporate. If there is too much condensation for that to work, then use a microfiber cloth to wipe it up.
If you somehow get moisture between the two plastic barriers that make up the lens then you are screwed. You will have to leave the lens somewhere for a while until that moisture can evaporate and make its way back out the porex filter (good luck... you might want to consider a replacement lens while you wait for this to happen).
There are anti-fog sprays or balms on the market (cat crap is a popular one), but in my experience, none of them work as well as the ones that are bonded to the lenses themselves. If you rub away the coating then the sprays/balms/etc will be your only option.
I keep a spare lens in my pocket and a spare set of goggles in my backpack. If lighting conditions change, then it is easier & faster to swap goggles than fiddle with changing the lenses. I only really reach for the spare lens if I have loaned out my spare goggles to a friend or happen to be riding without a backpack that day.
Read on another forum: "If someone held a gun to my head and said, "You have to move to Salida tomorrow", I'd probably do it. If they told me I had to go to Breckenridge instead, I think I'd just let them pull the trigger."