Wirelessly posted (iPhone: Mozilla/5.0 (iPhone; U; CPU iPhone OS 3_0 like Mac OS X; en-us) AppleWebKit/528.18 (KHTML, like Gecko) Version/4.0 Mobile/7A341 Safari/528.16)
Your Apps will still be available, but back them
up in iTunes just to be safe. Jailbreaking is reversible only by restoring your iPhone, but that shouldn't be much of a problem if you allow iTunes to make backups.