First, do you have a backup of your user data? If not please make one, two is better. That way you may do this without becoming unnecessarily concerned. 🙂
Second, do you have the 'retail' Snow Leopard disk that I provided a link to? When you get that, then I suggest that you start this process. Note, any other 'gray' Snow Leopard installation disk will not work because they are model specific.
The first link you provided (OSXdaily) is good in principle. The second one is a bit dated and not as good as what I found. Here is a link that describes just how to partition the internal HDD. A couple of points:
Select the HDD at the top of the left hand column.
Note in the lower left hand corner is a ? mark. If you get stuck or confused, that is the 'help' button.
http://www.geek.com/apple/how-to-partition-a-mac-hard-drive-1482555/
When you have partitioned the HDD, THEN you will install Snow Leopard using the white retail disk. Insert the disk into the DVD drive holding the C key. Follow the instructions. Note that there will be a pane where you will be required to select where you want the Snow Leopard OSX installed. Select the newly created partition.
After the Snow Leopard OSX has been installed, you will have to go to Software Update (Click on the icon in the left side of the menu bar). The Software Update will update Snow Leopard from 10.6.3 t0 10.6.8.
Then you will create a App Store Account:
http://support.apple.com/kb/HT4479
If you already have an Apple ID (for iTunes), I suggest you use the same one.
With the App store account you can select and download Mavericks from the App store. Note that it is a download and does not use a disk. A solid Internet connection will be required. Again when installing Mavericks, choose the partition where Snow Leopard has been installed. It will replace Snow leopard with Mavericks.
Any questions, please ask. Good luck.
Ciao.