I am pretty new to mac. I purchased this one a little over a year ago. Since I purchased it Apple came out with an updated or new operating system which I downloaded. A few weeks ago my hard drive crashed and I had it replaced. The technician said I should upgrade my 4GB of ram to 8GB because of the new operating system. He said it could be upgraded for a little over 100 bucks. Is this sound advice or is he just trying to sell me something I don't need?