Which steps do you mean?
I've also allways get the error "e: can´t open /cache/recovery/command" while I'm in the red triangle menu and pressing vol up + power, don't ask my why, I have changed to Linux/Android just recently.
What things have you done before you got the 2nd error?
After fastboot started up:
have you connected the phone to the pc (and gave your os time to install the drivers)?
What OS are you using?
If it's windows:
You must open the command prompt (right click in the unziped folder, while pressing the control key, and select open command prompt here, or open it via all programs, and navigate manually), and write the full name (step1-windows.bat) and press enter, because you then can read the messages from the program, and i think there's a smale difference in execution compared to just double clicking it.
@sunnycls:
If t-mobile hasn't released their branded OTA yet (don't know, tried update check?), then you either wait, or you root and debrand your phone, so you can install the generic OTA (you will lose root), or install the rooted update, send me a PM if need the link, stupidly I can't post links.