1. I know Yorkies can be yelpy, but are their barks loud enough for people walking by - outside of your apartment - to hear them? It's hard to tell from the videos on YouTube how loud they are.  
Well, personally, Maddy barks rarely.  She barks when she plays and when someone is at the door.  
2. Would the dog get stressed if it was consistently living in two different places? On the weekends I always go home to my family, so the dog would be home for about 2.5 days each week and at my dorm the other 4.5  
This could vary.  I think if you start this young the pup will get used to it quickly! 
 
3. How much do Yorkie puppies typically cost? I feel so uncomfortable looking for one to buy because the prices range anywhere from free, to $200, to $2000.   
When I have seen ads for $200 yorkies, they are scams.  You can get a pup for a more reasonable price, but you are looking at 800-1000 for a healthy pup, esp. in Cali. 
4. Does anyone know a good place to buy a Yorkie in SoCal, specifically within Orange County?  
Sorry, no. 
5. Will the Yorkie get stressed if I have odd hours at times? Sometimes I'm awake at 7 in the morning and go to bed at 1, other times not until 12 PM and staying up until 3 or 4 AM. It varies widly depending on the quarter at school. I would still be at my dorm for hours and hours each day though, so the amount of time isn't an issue, it's the time of the time. 
 Dogs usually adjust to your schedule.  This should be ok.  
6. Is this the basics of what you do with a Yorkie or any dog for that matter?: feed them, give them water, give them baths, brush and cut their hair, brush their teeth, wipe their eyes, give them shots and take them to the vet 1-2 times a year, pick up their poo until they are potty trained, walk them, play with them, buy them toys. (Yes I know silly to ask, but like I said I've never owned a dog before.)  
Please feed a high quality food.  (Innova, Royal Canin, Wellness, etc.)  You can find many reviews in the health/diet section of this forum.  Of course, lots of love and play time is important too.  
7. I'm going to Japan in July and won't be back until August 1. Will the month of August and half of September be enough time to train the Yorkie at my home and then take it to my dorm where it can be happy and obedient? 
This depends on the dog.  Yorkies are sometimes tough to train and they can be stubborn!  
8. What's the youngest I can get a Yorkie? 8 weeks?  
I think 12 weeks is the youngest.  
9. Frankly I think Yorkies with long coats are ugly (and girlie), lol. Is it normal to have them with short hair?  
Many yorkie owners keep their dogs in puppy cuts.  There are many variations to the puppy cut, and by looking around this site, I am sure you will find at least one you like.  And after you see some of the yorkies in their full coats, you will learn to appreciate the beauty of it.   I hope this helps!!