So I got my first Oranda goldfish today and he's amazing!  He's blue and gold, with a gorgeous wen.  Does anyone have any advice for me?  I'm an experienced fish owner, but haven't had any fancy goldfish before.

I agree with Andrea, post photos asap!

I've got two orandas as well, and they're not any different to keep than other fancy goldfish except that you need to be even more careful with their diet as they can easily get constipated if fed only flakes or pellets.
So about the food, you need to have at least 2 different kinds of staple pellets for your fish! There are special prepared foods for orandas available by Hikari It promotes their headgrowth and color Aside from this you'll need to feed it live foods, frozen, in gel, or freeze-dried. There's a great deal of live foods available, so please buy two different kinds of that too! Or more c: It'll last a long time anyway! I would recommend blood worms, tubifex, brine shrimp, krill and mussels You could buy the mussels raw and boil them yourself before you freeze them Always thaw any frozen food before you feed it to the fish!!
Next, you're going to need to feed the fish with some vegetables and fruits! Here you can be quite creative as most things are well accepted by goldfish. Shelled peas (Buy them frozen, thaw them and pop them out of their shells before feeding), cucumber, blanched lettuce, zucchini, spinach, carrot (might need to be boiled first) etc. Make sure there are no salts or spices present!
As for fruits, it'd be best to feed it the same day you'll be doing a water change, since fruits are very juicy and can easily foul the water. You can feed it bananas, watermelon, strawberries, orange and mandarin pulp, pear, peach and other slightly softer fruits Again, be sure that they're fresh and that there are no additives like sugar and the like! If you'll be sure to give your fish a varied and healthy diet like this, he'll grow big and healthy for you

I hope you're offering your little guy a 15-20 gallon tank (20 would be better!!) with decent filtration! In case you haven't noticed, goldfish are large fish that create lots of waste! Even their gills are creating ammonia, so you need lots of bio filtration in your tank! And a powerful filter that turns at least 5-10 times the volume of the tank! But make sure the current isn't too strong in the aquarium, because fancy goldfish can't handle too strong streams, even if their forefathers were river fish
Be sure to change AT LEAST 50% of the water in the tank every week or two weeks. The more the better when it comes to goldfish. That will keep the wastes from accumulating.

That's about it!! Now enjoy your fish