Possibly the best start would be to get hold of a workshop manual. Ebay has a fantastic range at times of the parts, you just have to make sure you have the money to bid on them. Maybe joining a Honda Goldwing club would help as the guys in them are great to ask advice from and might know places for you to source parts from. I know this as my father has been restoring motorcycles for over 50 years (all Engish bikes). Keep in mind if this is your first restoration you may be in for a bit of a shock as the prices of some parts can be expensive. My suggestion would be to buy a copy of Just
bikes and in the back of it there is a large listing of all the
bike clubs so just get in touch with the Honda Goldwing Club down there as they would have vast resources of information and help as the cross section of models would be large in their club.