ManOwar,

1. I would not recommend to anyone that their first venture into English double guns be from an auction house purchase. Its a minefield out there as outlined by the posts above and nothing beats being able to work out a purchase issue with a reputable dealer. Speak to Dig or Toby and they will give the right guidance.
2. You don't need 2 3/4in, 2 1/2 is just fine with the right shells.
3. Buy the condition and not the name.