Yay, tennis!!! I take lessons every Saturday
and have been for 22 years, now.
Yes, you can hurt your wrist, elbow, shoulder, back, knee and ankle. Ever hear of tennis elbow?
That's tendonitis of your elbow due to tennis. This is actually the most common injury when you swing around a real life tennis raquet. You can hurt your lower body as much as your upper body, because the movements are back, forward, left and right in a matter of seconds, and in random order, while swinging the raquet.
I'd say it's best to start out with lessons. Find a tennis school, and have an instructor teach you from the very basics. This is important to 1) learn good and effective forms that will last you you lifetime, and 2) to prevent unnecessary injuries. Correct tennis forms are the best way to prevent injuries.
What type of raquet is best depends on your grip strength and arm strength. It's best to start with light raquets, and progress to heavier ones as your strength increases, but unless you are a professional player, for women, the second lightest is the limit in most cases-- as is mine.The tension of the gut strings (how strong it is strung) is as important as the weight of the raquet. Another thing that is important in choosing raquets is the material of the raquet. Wood is no longer in use, present day raquets are a combination of light weight metals and graphites, but depending on the ratio of the materials, the flexibility of the raquet differs. This flexibility is just as important as the weight of the raquet and in fact, also influence the tension of the gut. You need to get the best combination--raquet and gut--to prevent injuries. A good instructor can advice you on which raquet is best for you. Tennis schools here often has raquets that they lend to beginners for the first lesson or two, to see what's best for the person, and advice them which one to get, and which gut string to choose, have strung at which tension. This way, you won't waste money by choosing a raquet that isn't right for you.
Since you are a beginner, a light weight raquet that is flexible and the gut tention soft would be best. The tension can be made higher as your tennis lessons advance, and your techinque and strength improves.
The rules aren't that complicated. Basically, so long as the ball lands in the court with one bound, it's in play. There are two side lines, the inner line the limit for singles, and the outer line the limit for doubles. Service shots--the first shot that starts the game, must land between the net and the middle square on the same side that the receiver is positioned--in other words, diagonally from you. The entire game comprises from either 3 sets or 5 sets. One set is at least 6 games, the one who wins 6 games first, with the difference of at least 2 games, wins the set. In other words, 6-0, 6-1, 6-2, 6-3, 6-4. There is no 6-5, it has to be a 7-5 win. There is a rule called tie-braker, which is applied in many tournaments to prevent the games from going on forever when the difference in the won games within the same set is only one game. The points are counted, love (0), fifteen, thirty, fourty, and when you win your fifth point, you win the game. If the score is even at fourty-fourty, this is called duce, and you need to win two points in a row to win the game. When the score is duce, the next point is called "advantage server" or "advantage receiver" depending on who won the point. When the person who has the advantage wins the next point, the game goes to that person. The servers of the games change within the set, and the players also change sides. This can look confusing. If you win the game that you are serving, that is called "keeping the game." If the receiver wins the game, that's called a "break".
Have fun, tennis is fun, and you can play into old age--my parents played into their early 80s before they quit.
Anybody Plays Tennis? 
So long as you are putting your best foot forward, then, 
KB
Linear Mode
