How can I change my eyes/face from downturned and sad to upturned/happy looking? (photos)

You are referring to have more almond shaped eyes. That requires elevation of the lower eyelids, NOT just canthoplasty. That is critical to understand to achieve natural results. 

Here are the key differences between you and your wish photo: she has a higher nasal bridge and also double eyelid creases with a more wide open eyes.  To achieve something similar to the wish photo, you would benefit from epicanthoplasty to widen the horizontal dimension of your eyes, double eyelid surgery to give you a more defined crease, and some form of nasal augmentation, either from fillers or a more formal rhinoplasty.  Hope this helps.

hi,
based on your photos, you are very young and you should not have a weak lower eyelid and i believe it is how you took your pictures....if you do not have a true neutral chin position and your chin is tilted down and your eyes are looking straight or up, you will see more of the "white" of your eyes.  to change your eye shape, you are a good candidate for Asian double eyelid surgery.  i suggest for you to see a board certified plastic surgeon who does mainly Asian eyelid surgery for a consultation.  hope this helps.