1. Yes, they "should".
2. Yes, they don't care what device you have as long as it is a GSM network BB. Otherwise, it won't work anyway if it is not.
3. Yes, if the previous owner has released the PIN/IMEI from the previous carrier (Rogers??). If not, they will need to do so.
4. You will be using TMo Service Books, since you will be paying for TMo service and BIS.
Read this: Buying a BlackBerry off eBay - BlackBerryFAQ
My best advice, make sure the BB you are buying is fully returnable and/or you are able to get your $$s back if the PIN/IMEI cannot be released from the previous carrier. Often, lost or stolen BBs have been locked from being used elsewhere.