I've not come accross anyone when reading through lots of forums etc who has managed to totally "brick" their iPhone ( make it unusable ) unless it had some kind of hardware fault.
If you look on this forum there are loads of "help! i've got X wrong with my phone" - and if you look at this kind of thread you will see that normally the problems can be solved by re-installing the firmware of the phone through itunes.
We don't change the operating system of the iphone ( not yet anyway but it is possible I guess in the future ) we just modify what is already there.
Hope this helps.
You may start reading about "Jailbreaking" and there is looooooads of information out there on it. You may be better off however by just looking for "pwnage" instead. This is a new technique which may be a lot easier for a new person to work with. Read up on it while you wait for your phones to arrive from ebay
