So, the first thing to address is your question about your processor. There is a >90% chance that you do not need to replace your processor and that your processor will remain good for the next 4-5 years, sans any major updates to the CPU industry, which is highly unlikely. With that being said, there is never a guarantee without data, so if you would like to take the time to learn a little about what your system is doing, you can monitor how much of a workload your computer is working with.
Assuming that there will be multiple people who read this and may have a similar question, I'm going to suggest a rather simple tool called
Open Hardware Monitor. Please note, however, that not all processors are supported, but you can see what processors are supported
here. If you happen to find out that your processor is not supported, you could also try
HWMonitor, which has a wider list of
compatible hardware at the price of not having as much information and also being attenuated compared to it's pro version. Once you begin using it, you will see how much your CPU uses in power, and if it is using moderate-high amounts of power, you may want to look into a new CPU.
Now, for your second question regarding both your GPU and CPU and running GTA V, you will be fine. If you would like to know if you are okay with any other games, you can use
GameDebate's Can I Run It? tool. I took the liberty to fill out all of your perceived specifications and get you the results you were wondering about. You can find that information
here.
I do want to take the time to say that I am not affiliated with any of the companies/organizations that were linked above, and I also do not take responsibility for the links that you click on. This is only a disclaimer and is not meant to scare you away, only meant to remind you that the only person responsible for your internet safety is you.