Can I program blank transponder keys to my Cadilac STS 2005 without the master key?

My brother gave me a broken down Cadi STS 2005 with only a door key and no transponder. This is one of those, "if you can fix it, it's yours" kind of deal. I don't really want to dish out $200 to Cadilac for this key just to get the car running, but I'm reading that as long as I have a key I can program any blank transponder to the car. Is this true? I want to believe the following e-how:

http://www.ehow.com/how_7314562_program-remote-sts-cadillac.html

but there are other forums that say if you lost the master key, only a dealership can program. The dealership called this key, "the valet key".
(I'm not sure why it's called a valet key given that this key alone isn't enough to power the vehicle..)

As a student, Cadillac part prices are ridiculously high so obviously I'm trying to cut corners here!
I should add, the main reason I want to avoid the dealer is because I'd be required to get the vehicle to the dealer. Car is broken down, which means I need a tow truck TO and FROM the dealer. $200 + the towing is an expense I'd like to avoid. I intend to fix it myself.

Thanks !

The Ehow thread is for programming the RKE (Remote Keyless Entry) Transmitter (Key fob)
What you need is the TDM (Theft Deterrent Module) Programming procedure.
Unfortunately This vehicle can only be programmed with a Factory GM TIS software or can be done by a locksmith with the correct software.

NOTE: The locksmith will come to you (That is one saved expense)

ADDED: Cadillac is not a "Cheap" vehicle to maintain.

The valet key will run the car, but not open the trunk where you keep your furs and jewelry safefrom the valet. You need the original key to recode a new key if you have a key coder I will not say where to get a coder. The dealer can code a new key and some lockesmiths can do it as well- some are a little cheaper than the dealer. Try the "ehow" method. They're usually pretty good. Better print it.

Heck yeah Cadillac parts and service is sky high.