iPhone 3G Unlock Question

[mike868y]

Hey everyone, I am currently under a T-Mobile contract and have an opportunity to buy an iPhone 3G for a cheap price. I plan on unlocking the phone to use with my T-Mobile SIM. However I have a few questions.
1)If I plug my phone into my comp and reload a fresh OS 3.0 install, will everything work alright w/o an ATT Sim?
2)Once I run the redsn0w program to jailbreak the phone, how will I install ultrasn0w via cydia or icy? I won't have a T-Mobile SIM in it and my T-Mobile SIM will not work yet. Will I be able to install these apps over wifi? Or is it common practice for people to have an active ATT SIM while unlocking.
3) How is voicemail handled on unlocked handsets? Will I be able to use visual voicemail?

Thanks so much for your help!

[i.Annie]

1) It's not gonna work without an ATT sim. But restore/upgrade to 3.0 anyway, because JB will fix it.

2) Running redsn0w, make sure you don't install Cydia and Icy together. Just install Cydia. Go into Cydia when you're finished with the JB and go to Manage>Sources>Edit>Add and enter repo666.unltrasn0w.com/ (last O is the number zero) then install it. Go back to Cydia when it's done and tap on the repo you just added. Install ultrans0w.

3) VM is located in the Phone app on the bottom right corner. Tap it and it will dial and access your VM automatically. Visual VM does not work for T-Mobile, only for ATT customers.

[mike868y]

Thanks for the info. I can't wait to unlock my phone and get away from my slow/buggy blackberry haha.