Prayer doesn't have to be verbalized
If it's hard for you, just move your lips but don't make noise. I have to do that sometime even just doing reading for homework!
praying is a great thing, because you can pray any way you want. you don't have to hold ur hands, you don't have to say it out loud, you don't have to be like some religions and kneel down, and bend, and have like an arobic excersise. you can of course, but you don't have to. you can pray whenever, and however.. God knows when it's directed to him!
Yes, you can pray the rosary silently, and sometimes you should do so, before Mass, for example, when you decide to pray the rosary but other people read, pray silently or meditate.
True. There's nothing wrong with unverbalized prayer, but it can make it harder to contemplate the mysteries. That's why I'd suggest whispering the prayer: you won't make any noise, and it shall be easier for you to meditate.