Needing to get a new cpu fan/case fan

I've had my PC for about 7 months now and I think my CPU fan is on it's way out. It hasn't been running properly and I've had to actually open my case and start it manually for it to actually spin. I figured rather than dealing with the company and asking about a replacement for it I should just buy a new one since they are relatively cheap. I know almost nothing about fans, and the most I know about my own is that it's a 120mm.

What could anyone recommend as a replacement to this, and should I get two of them? I don't know if I'll need two of them for when it gets warmer, I figured it would be better to just get more fans that will cost me about 60$ rather than having to spend about 200$ on a new CPU if it were to overheat.

As of right now my case has two fan located one at the front and one at the back both of them being an exhaust. I have one more space for a fan at the top of my case. Would it be necessary for me to get one, and if so would I need an exhaust fan or an intake fan? Also size would I need for it, because as far as I can tell the space is much larger than that of where the two exhaust fans are.

CPU: Intel Core i5-2500K 3.3GHz Quad-Core Processor
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler
Motherboard: ASRock Z68 Extreme3 Gen3 ATX LGA1155 Motherboard
Memory: G.Skill Sniper Low Voltage Series 8GB (2 x 4GB) DDR3-1600 Memory
Hard Drive: Western Digital Caviar Blue 500GB 3.5" 7200RPM Internal Hard Drive
Video Card: EVGA GeForce GTX 570 1.25GB Video Card
Case: Cooler Master HAF 912 ATX Mid Tower Case
Power Supply: Corsair 650W ATX12V / EPS12V Power Supply