Yea you should be able to just upgrade your Mobo, CPU and Video Card also you may need new RAM depending on how old your old Mobo is it may not support older RAM chips. Since this is your first build I suggest going to Newegg and buying a package mobo/CPU that way you know you are purchasing the right mobo and cpu that will work together. If you do purchase new RAM make sure you look at the speed of the RAM and you will need at least 1866 MHz speed for BF4. you will also need to look at the mobo you are purchasing and see what type and speed RAM it supports.
i have 6 gb DDR3 ram and my motherboard is SX2110-ER2 lmao old school motherboard dont know if i should use it or not but supposedly the motherboard is locked to the windows i got now and it is a gateway so i think ill have make a new rig or something xD!!