Should I purchase a PDA?

Can someone please tell me where I can purchase a PDA? What type of store would I go to? (I do not want to purchase on line) Do I need to subscribe to a service plan? Are there specific PDAs for nurses and do you have to download information? Sorry...So many questions...Any help would be greatly appreciated as I am starting a new job on Tuesday..(My first nursing job since my graduation in 2008) I'm thinking that a PDA would enable me to look up information rather than asking someone everytime I have a question.
Thanks, I am somewhat technologically challenged...