|Congratulations! You have just adopted the most loving creature on the entire planet. Caring for a chihuahua is the same as any other animal in that they need food, shelter, vet care, etc.
The difference is that this little critter will want to be with you 24/7. Unlike hounds, retrievers, spaniels, labs, german shepherds, etc. a chihuahua'sjob is to love their human. That's it, their entire life is devoted to the love and adoration of one or two people. They will be content to lay next to you or on your lap (or on your shoulder) for hours on end, and usually get all they exercise they need running around the house. Like cats, they are very fastidious, cleaning themselves frequently. If you have more than one, you can often see the others cleaning the dominant dogs ears and face. Also like cats, they like to be up high, on the back of the sofa if possible, and will sunbathe for hours in the smallest patch of sunshine.
You will have to make sure she understands that you are alpha, spoiled chihuahuas can easily become the nasty snippy yippy dogs so many people think they are. Don't accept any behavior from her that you wouldn't from a 60 pound dog. Jumping up on people, growling after you have let someone into your home, snapping, etc. are not cute, they must be dealt with just as you would a large dog. A well behaved chihuahua is a credit to her breed, as well as to her owners.
The reason Chalupa whines and kisses your face most likely is that she is So Happy that you are paying attention to her. In the wild, licking an adults lips is how puppies ask their mother to regurgitate meat for them. In adult dogs, it remains as a submissive gesture, symbolically asking for food means "I acknowledge that you outrank me". It Does Not mean you need to feed her. She loves you and is telling you that by giving you kisses. She can be taught "That's enough" which means what you are doing was ok for a while but now I want you to stop. I would discourage you from trying to break her of it completely. They adore their humans unconditionally and are miserable when they aren't allowed to demonstrate it.
Chihuahuas are very sensitive to cold, they like to have a blankie to curl up under, even when we humans are sweating. They love to be under the blankets on your bed, under your discarded clothes on the bedroom floor, under the pillows on the couch. It is important, Do Not Sit Down on any surface that has a blanket, afghan, jacket, whatever on the seat unless you have visual acquisition of the dog. Sitting down on a chihuahua can be fatal, no matter how thin you are.
As Minnesota is not chihuahua friendly 7 months out of the year, mine are both litter box trained using a regular pan and clumping cat litter. They are very fastidious and may require you to clean the pan every day. My little one will go to the litter tray and if it has more than two pee pees in it, she will look up at me as if to say "You want me to go in there? It's Dirty!". Once I remove the clumps and smooth the litter, she happily hops in and does her business. They also will go outside in the warmer months.
Chihuahuas eat small meals several times a day, keep dry kibbles out all the time. They suffer if fed only once a day, as they burn off so much energy but have such tiny little tummies. They will not eat until they are fat, once they realize that food will always be available, they self regulate very well. The majority of fat chihuahuas get that way because their owners give them too many treats, little tiny slivers of chicken or cheese are enough.
Chihuahuas often don't have any concept of how small they really are. They will defend their territory and their humans, which makes them great watch dogs but very bad guard dogs.
Get the book Chihuahua for Dummies, it is by far the best book I have ever seen on the care and feeding of these adorable little creatures. Chihuahuas are not dogs, they are little children in fur coats. They crawl into your heart just as human children do, and since they often live into their late teens, it's not that much different from raising a child, except your chihuahua will never talk back to you.