You can calm down a bit as its not quite as bad as it first seems.
Yes you will need another TWICE unit together with at least one key for that unit. The TWICE sits under one of the front seats and controls the immobaliser. Your own TWICE will now not work and you cannot program a new key to your unit unless you already have a working key.
There is a service in the States where you can send them your TWICE unit and they will programm new keys to your unit which you then re-fit to your car and away you go! But its as expensive as you've already been quoted so may not be an option.
The cheapest route is to buy a used TWICE with at least one key, check ebay and local breakers. Also get a new key cut to your locks by giving a dealer your VIN number.
Then install the new TWICE under the seat, very easy to do.
The car will not work. You have to have it programmed with a Tech2, its a simple job but only a dealer or Saab Indie will have one. Unless they do house calls you wil need to get the car to them.
When they program it get them to program the new key and the key supplied with the used TWICE, that will mean that you will have one working key that will operate the locks, otherwise you will have to change the locks (that is expensive). The other key will not operate the locks but it will operate the immobaliser. If you can afford it get two new keys cut so you have a fully working spare.
Its a lot of hassle but there's no other way to do it.
P.s If your car is currently locked you will need a new cut key from a dealer anyway to open it, it will open it but won't start it.