Just be gentle. There are clips on the GFX card(if installed) and most all of your power cables that are attached to the motherboard. Those need to be pressed prior to removing them from the board. Be very gentle with the wires coming from the front of the case that plug into the board. Those are called leads. Most leads are marked
http://i.fixya.net/uploads/images/66ce2fc.jpg with information that tells the user where each lead goes. Without those markings installation can become a chore. Some marking can be removed with too much handling. Just be careful. There are normally 6 screws that attach the board to the case. The included manual should be very helpful getting that new motherboard installed. There are orientation marks on your CPU and your motherboard. Pay close attention to the corners. One should have a triangle(or circle)
http://www.pcstats.com/articleimages/201206/installAM3HSF_22.jpg or the corner of the CPU may be angled differently from the rest. Install it another way and there will be issues and an unhappy installer. Make sure you know your case. Does the case have a cutout
behind the CPU? If you are buying an aftermarket CPU cooler such as the 212 Evo you will need to install the support bracket beneath the motherboard as shown in that pic. IF that doesn't exist you would have to have the motherboard outside the case to install the CPU cooler. If you have a stock cooler the motherboard can be installed first and no cutout is usually necessary.
Just plan each step and visualize it before you actually do it yourself. Never force anything. The RAM modules have orientation slots which show the user how they should be installed. The motherboard manual will also tell you how to install the RAM and which slots they should be installed in if all slots won't be populated.
Like the others have said re-installation of Windows is normally a requirement when changing out motherboards. You can change RAM, HDD/SSD, GFX, PSU, Case/Chassis/Cabinet) or any other part of your PC without affecting your Windows validation. When the motherboard is switched out then Windows see that as a new PC and the serial key is usually invalidated.
And of course the community is here should you run into any issues you need some help with.