Thank you for up voting! So i was able to add the missing links.
1. Download the OS X 10.9.1 Mavericks installer
As you may noticed, the apple app store denies the installation of the OS X upgrade caused by the lack of hardware compatibility. But we want to download the installer anyways. A possible solution is to run the download enabler tool. You can find it at the following place Mavericks_download_enabler. Extracting this zip file and running the executable with admin privileges disables the hardware check for the mavericks download in the app store. After reboot you should be able to click install. After giving an Apple-ID (which do not requires a credit card id) you should start the installation. This first downloads the installer (~5.4GB) and afterwards give you the first installation slide. At this point you can cancel the installation. The install package resides in the application folder.
2. Create a bootable installation usb drive
I used the tutorial bootable installation usb drive. The mentioned way using the command line tool, does not work for me. But the long way does.
3. Enable boot possibility for 32bit EFI bios
As mentioned by tiamo in this forum there exists an EFI 64bit to 32bit wrapper. You have to download the "boot.zip" file from the forum above and replace the boot.efi (which is content of the zip file) with the boot.efi files located on your bootable usb drive at:
4. Modify OSInstall.mpkg to disable the hardware check of the installer
When you try to boot at this point the installer from the usb drive, it should be able to boot up. But you will notice the installers message that the current hardware is not supported. Therefore we have to got rid of the installers hardware dependency check. The problem of often presented ways are, that you need a software called "flat package editor" which is available as a part of "X-Code". So you need access to X-Code which is not available under OS-X 10.6.8 directly from the app store. So i found a workaround to extract the mpkg package with the pkgutil command line tool.
4.1. Copy the OSInstall.mpkg
Copy your Packages/OSInstall.mpkg from your bootable usb drive to your desktop.
4.2. Extract the mpkg file by using the command line pkgutil
pkgutil --expand ./OSInstall.mpkg ./OSInstall
The first lines above let you go to your personal desktop folder. Please consider to replace <yourLocalUserName> with the username you are using on your Mac. The second line extracts the install package to the folder "OSInstall".
4.3. Modify OSInstall.mpkg
Modify the file inside the OSInstall folder on your desktop as shown in this youtube video.
4.4. Create the modified mpkg package from your modified folder
First you should remove the existing unmodified OSInstall.mpkg file on your desktop. After that you can create the new package by running the following commands:
pkgutil --flatten ./OSInstall ./OSInstall.mpkg
4.5. Replace the modified OSInstall.mpkg
Replace the your modified OSInstall.mpkg with the unmodified on your usb drive located at packages/OSInstall.mpkg.
5. Install OS X 10.9.1
Warning! This way of installation is not officially supported. So please backup your data in front of upgrading!
Reboot your system with your connected bootable usb drive, which contains the modified installation system. While booting your Mac hit and keep pressing the alt key until you see a boot selection screen. At this point you can choose you usb device to boot the OS X installer. If all previous steps are done correctly you should be able to install the system, like it is a supported one. You do not need any additional bootloader like chameleon. Please consider that the current Nvidia drivers are supporting only devices greater or equal than the Geforce 8 series. So you will see the correct desktop, but you do not have hardware support rendering the window effects stuff, when you are running the stock Nvidia 7300GT.