@ amnesia
800 is without the contract (buy the phone)
200-300 with contract (buy on installment including paying the bill)

before u jailbreak , you can always backup your contacts, SMS, bookmarks,music , email information(setting),pictures an watever u had in ur phone , just by 1 click in iTunes .
so don't worry about that
themes are always available in Cidya(which is not available until you jailbreak) :b

I think this is your first time to have an iPhone if u don't know this much.
anyways u sound excited ,,
u can get ur iPhone from voda,, its ok,,,
peace