is it just a matter of removing the sim from the existing phone, putting it in to the unactivated 2760, turning it on and voila? Is that all I have to do

Yup. That's the whole point of the SIM.

other than reprogram her address book

Another option is to save the entries onto the SIM. Then they'll get moved with the SIM. The procedure to do the save depends on your phone model. It should be in the manual or online via Google.

As for the other phone, should i just delete all the address book entries and try to flog it on ebay with the new sim from the 2760 and the phone number that came from the 2760?

You can do that. There may not be much of a market for older phones so bundling could be a problem for some buyers. Alternatively you could sell the SIM separately. It will be valid for at least 90 days and has $5 credit. The buyer can use it with any unlocked GSM phone and buy more airtime themselves.

As for the old phone, it may be of interest to someone whose GSM phone has broken and they just need something they can use until their current contract with Rogers or Fido runs out.

In any case, better than just erasing address book entries, look for a menu option that's called something like "Reset to Factory Defaults." That will erase everything, including call history, saved messages, etc.

a renaissance man indeed.

They had cell phones in the renaissance? Thanks for the kind words.