Boot d-i and install Debian in the same HD

[MaTa <emfamandraescriure@gmail.com>]

Hi

I'm Oriol Matavacas, a Computer Systems Degree Student. First, Sorry
for my English, I'm from Barcelona.

I'm testing a new type of installation. Please I need your help.
Can I boot the Debian installer images (through GRUB + initrd.gz,
vmlinuz) (initrd.gz and vmlinuz from hd-media, casper or the
"original" from debian installer), and install Debian in the same
hard-disk?
I would maintain the partition where I save the installation files
(initrd.gz, debian packages, all nedded) (in /dev/sda1 partition for
example), and install a Debian system in another partition at the same
phisically disk (/dev/sda2 for example).

Can I "skip" the partman/partitoning step?
How I can modify the udebs needed to complete the installation?
Where I can find more information?

Thank you very much in advance.

If you have any question, please don't hesitate to ask.
Oriol