Some of the newer Nokia models allow you to set up distribution lists for sending text messages but this is a relatively new feature. Whilst older models allow you to send "multiple texts", you still need to manually select each name and wait for the message to send before proceeding to the next individual. It would certainly be very time consuming in your case.
Unless you can obtain a new model like the 6230 that supports distribution lists, I would suggest that AMc's suggestion above is probably your best bet for large scale messgaing.
To answer your question on the 3310, no, there is no internal phonebook memory - all numbers, and messages will be stored on the sim card itself so phonebook size is limited to the number of spaces provided by your operator (in some instances as little as 100 names

)
Hope this is of some help to you...
K.