What year? You didn't say what year, but I have an '89 wing and it has a drain plug located at the bottom center of the engine (sort of straight down from the leading point of the seat, under the bike). It's easier to drain the oil if you can get your bike up on it's center stand.
The oil drain plug is on the front of the motor below the oil filter.
Take front fog cowling off. remove drain plug, and remove oil filter.
Oil drain plug is located at the back of the engine, right side, ( foot brake side ) towards the bottom of the engine.
Under oil filter, a little to the right. 17M size head on bolt. Look under radiator.
The oil drain plug is located on the underside of the engine directly below the filler hole. The head of the bolt will need a 17mm socket to remove.
There is a plug on the engine right beside the oil filter. This will drain the engine and rad. Or, just remove the lower rad. hose at the thermostat.
If you look at the diff. you will see a drain plug and a re-fill plug. Check with your local dealer for the right oil.
No
Yes, it is. However, there is separate gear oil in the final drive of the Goldwing, as it is shaft driven.
same as the engine oil
My owners manual for my 1984 Honda GoldWing says to use SAE 10W-40 Oil.
Yes you can use a Full Synthetic Oil in your GoldWing. I recommend Amsoil 10W-40 Advanced Synthetic Motorcycle Oil (MCF) Hope This Helps