A month isn't neccessary. You could learn all you needed in a night if you really committed to it.
Every time you install a piece of hardware, (a physical, tangible item), into your computer, it needs instructions on how to interact with the rest of your hardware. These instructions are called drivers. So in order for your motherboard to communicate with your Video Card, your RAM, your Harddrive, your Processor, your CD Drives, it needs these 'instructions' or drivers. The motherboard you buy will come with a CD containing these drivers. Simply pop it in and install them.
If you change usually 3 or more pieces of hardware in your computer, you will need to have one of those Window CD's that you recieve when you buy a new computer as you said. However if you change the Harddrive then yes you will need to insert the Windows CD again. This is because that CD transfers the information on it to the harddrive. So by changing the Harddrive, your computer no longer contains the information that it originally obtained from the CD.
I would reccomend reading this, 'How to build a PC' article in its entirety. As that is basically what you will be doing. You will have to remove all the pieces of hardware from your current motherboard, then take out the motherboard, then place in your new motherboard, then reattach all your other pieces of hardware.
This article lists all the pieces of hardware in your computer, and what they do. Read this first.
This article explains how to put these pieces together with detailed pictures.
After reading those two articles post anymore questions that you have regarding anything. There is no such thing as a stupid question. Practice tinkering with an older computer if you have one laying around.