Help with modification on the Debian installer (tasksel)

[nidr <drnlk2a@gmail.com>]

I want to modify the Debian installer. 
So I've downloaded the source of tasksel 2.23 and made a deb from the
source with the "dpkg-buildpackage -rfakeroot" command. And replaced my
"unofficial" tasksel_2.23_all.deb file with the original one in the
pool/main/t/tasksel directory on my sarge iso.
So I thought this would work (just for testing purpose atm), but I get
an error under the installation procedure "Installing the Debian base
system":
Validating tasksel...
Debootstrap Error
Couldn't download tasksel.

I've updated the md5sums.txt file with the command "find -follow -type
f` > md5sum.txt"
I've also updated the md5sum in the Packages.gz files located in
dists/sarge/main/binary-i386/ and dists/testing/main/binary-i386/
What am I doing wrong?
I haven't modified the source at all, just made a .deb out of the
original tasksel 2.23 source.

-Thanks for any input.