1st thing is you dont extract a .cab file, you simply transfer it to the phone and run the cab file from there using file explorer.
2) did you unlock your TP2? by unlock i mean did you run hard-spl
(did you follow these instructions to unlock your phone?
http://forum.ppcgeeks.com/showthread.php?t=93252)
3) if you properly unlocked your phone following the instructions in the link above, you can now download a cdma rom (assuming you are still with sprint) and run the exe (probably named "Custom_RUU.exe" or something along those lines)
and just follow the instructions on the screen and next thing you know you will have a new rom on your TP2
enjoy