1. Will I lose any data currently on the phone? Is there anything I need to do to protect it?No, but I would backup/sync your iPhone on itunes before starting.2. Now, to reverse a jailbreak all it says I need to do is restore default settings, but I'll lose everything then, right?You don't have to restore to reverse the jailbreak. If you upgrade to a new OS, then it will rreverse the jailbreak. I think that's why, in part, Apple keeps coming out with a new update seemingly every few weeks. I just read that OS 4.3.2 will be out soon, so if you jailbreak 4.3.1, then you shouldn't update to 4.3.2. If you read what each new update does (fixes some bug, adds some protection, etc.), they rarely do anything earth shattering with each update. I read the 4.3.2 update will only fix some bugs related to the Verizon iPhone (which may or may not effect you).Even if you have to restore your iPhone, so long as you've recently backed up your phone on itunes, you will be able to put all the information, apps, settings, etc. back on your phone.3. I am not on my home computer, but at work. Will this work if I don't have iTunes on this PC?I don't know, but I'd guess that it would work because I didn't have to use itunes at all when I was jailbreaking the phone. I did mine on the computer that has itunes.