if u add the SK data, u have unlimited data and text messages... u dont recieve picture messages on the SK...they send u a text telling u u have a pic message and to log on to the new to download the pic...i think u should be good with just ur myfavs 300 and sk data.
and u should be able to do them at the same time, just when u log into ur acccount online, change ur phone to the sk3 or whatever u have then when u go to add the services, you will have the services available to u such as sk data...if u have registered ur phone online as a bb 8100 they will not offer u sk data, thats why u need to change ur phone.