adding multiple users, newuser? and vim

[Mike Egglestone <megglestone@heritage.sd57.bc.ca>]

Hi

I have a txt file in this format:

joe blow
john smith
john doe

I would like to use "newusers" to add about 500 accounts to my system,
but how do I quickly make the txt file look like this:

joe_blow:password:1001:1001:,,,/home/joe_blow:/bin/bash
john_smith:password:1002:1002:,,,/home/john_smith:bin/bash

or
jblow:password:1001:1001:,,,/home/jblow:/bin/bash

Is there some good vim commands that would allow me to add 
the extra stuff that "newusers" needs in order to add the accounts?
Or is there some better way to add accounts from a txt file?

Thanks for your help!!
Cheers,
Mike