You will only notice a performance improvement if you haven't got enough RAM to use the applications you need. If you had a lot of free RAM before, you won't notice any difference now.
If you already have your computer, you can only replace the processor if you replace the logic board. Your computer requires a specific logic board, so you shouldn't replace it and you have to stay with the same processor. Apart from RAM, the only part you can upgrade is the hard drive. What will make an improvement is a SSD drive, if you haven't got one