Of course they are, as long as you do not damage your card during installation, and do not lose any parts, like screws and such.

Be aware, some folks report that their thermal pads that come on the card do fall apart when the air cooler is removed, so do your best to be gentle with them, and try to keep them preserved as best as you can. Other than that, you will just need the stock cooler on the card if you ever need to RMA, so make sure you keep that cooler close by.