Ok...
pawoolon...
you wanted to know if you were about to do something stupid..
well...
I wouldn't go so far as to say such words...
But...
ok...
you are about to do something stupid.

the wayback machine has everything you need firmware wise to do all that you need to reflash .

Go there.
the official builds are there.
other people's "saves" of this repository are nice...
I have them saved myself...
but it is unnecessary as long as the official ones are available...
I suggest you go there ...download them and save copies of your own in a storage ...for the future...as much as the present.
I do not suggest trusting someone else and any possible tampering they may have done.
As nice and reliable as they may be...
You don't know.

justmemory's link ..
http://maemo.muarf.org/tablets-dev/nokia_N900/

is the self same link to the archve..
http://skeiron.org/tablets-dev/