A barrel change is all it should require. Once the barrel is off though, a good 'accuracy' smith should true up the action and lugs before going on to the barrel. Get a good barrel done right and you won't regret it.
However, I will point out that if you shoot high BC 7mm bullets and neck size your cases so you headspace off the shoulder the 7mm gives better ballistics with a little less recoil.
If the 300WM barrel is in good shape,I might be interested in it,The 7mm is a great round,but I like my 300WM,besides,I'm up to my neck in brass,.30 cal bullets,dies,etc.