[otrs] newbie question: how to change ticket 'subject', 'from' or 'status'

Hi all, Sorry for the extremely basic newbie questions: having installed OTRS 2.0.4 and got it basically working, how do I (an agent) change: - the subject of a ticket, suppose the user has been massively inaccurate or left it blank. - who the ticket is from, either replacing the originator's email address entirely, or perhaps adding a second person to the "from" or "interested" set? - the ticket state (obviously "close" closes it, etc) but how for instance could I (an agent) reopen a ticket after closing it in error? I have checked through the last 2 months of archives, and of course read the admin manual from cover to cover, before asking these questions... cheers duncan