AMD list a 450W as a minimum requirement. For these 3 months, have you had any artifacts of shut-downs? Also, how many amps do you have on the +12V rail? (you can check that by opening the case, the PSU has a label on the side)
OK, so what you have there is a 450W PSU. I couldn't find exact specs for it, but if it's held its ground for three months it should be fine. However, it's a cheapo PSU. To be absolutely sure you'll need 500W and more, but those cost $50-70 (rs. 3000-4000). It's not that much and if you can spend $60 on this for example:
Yes, do that. If you are going to only play fifa, you won't need a more powerful GPU, so now you only need to worry about the PSU to support it.
As I said, it's doing very well so far since you haven't had any shut-downs or artifacts. No need to cahnge it now. But if you see any of the symptoms of a failing PSU- overheating, shut-downs or artifacts, change it immediately! Do not wait as it will damage your GPU.