Hi!
That is what you do....just take the engine apart and warm the housing ( I use a propane torch instead of the owen ) and the ballberings will fall out when tou hit the housing on a piece of hardwood. Simple ? Yes!
Ballbearings could be bought from any ballbearing dealer...see to that you get C3 competiton play in your bearings as this gives more rpm than standard ballbearings!

Regards!

Jan K
Pylonflyer from Sweden