I would X brace the openings before you remove the offended tins for replacement ..the doors wont hold much as they latch only only on the striker.
I suggest removing the doors tack in your braces ...an then go for removin the floor, also get the floor in before movin on to the firewall ..try an keep it as sound as you can as you proceede, to keep it as square as possible ...Im sure there will be some gents chime in with LOTTS MORE KNOWLEGE on this.
just go slow.
Tim
