shaft
There is NO WAY to do this swap without dealing with those needle bearings. I have a decent pic of it and will help you change it because it is easier with 2 people but as I said there is no way around removing and then putting back the 120 needle bearings. Ought to go ahead and change the chain at this time since you have it apart. Also there are 2 "C" clip type retaining clips that are a real pain to remove without the proper tool. Holler when you get ready to tackle it.