I read a hack to use a T-Mobile SDA for skype, and how to unlock the SIM to use with any carrier...
 
I have Verizon, and I'm stuck with verizon...
 
Does verizon use SIM cards, so that i can use my existing number/plan on the T-Mobile phone? Or am i pretty much SOL like i think i am...

Verizon does not use SIM cards. All carrier recognition is done one the handset, and handsets are attached to accounts via the ESN of the handset. However, there are similar hacks in existance with the XV6700 (HTC Apache, check it out here) and also probably will be doable on the XV6800 (HTC Titan) which is coming soon (read: Q1) to VZW.