Whole milk is a new experience when compared to BM.
I would recommend introducing it in small amounts in cups at meals and snack time and continue to allow him to nurse regularly, as desired. As with any new food, you'll need to continue to offer the whole milk until the pallet adjusts. This may take several days so be patient. Once he is drinking it regularly and meeting his hydration needs with it, he will (most likely) naturally start to loose interest in the BFing and more than likely "self-ween". I recommend going with a cup that has a straw (like a munchkins cup) instead of a sippy cup with a valve (like Playtex cups have) since the sucking of a straw is more similar to nursing action.
Make sure the milk is fresh each time. Also, he may not like it ice cold since he is use to nice warm body-temperture BM. You may find warming it helps a bit.
Lastly, do not confuse the issue by putting whole milk in a bottle. We had/have very strick rules about this in our house - if we were transitioning to whole milk that was always offerred in a cup. I think this method helps with weening in general - from the breast or from a bottle.
Good luck.
~C.