What makes them think your hard drive is bad? If it's from 2014 it's totally within the drives working lifespan. So unless there is something actually wrong with it, such as damage or reporting bad s.m.a.r.t values, I don't think there is any reason to replace it. Of course hard drives off any age can fail, so it's always good practice to keep a backup of important data. Hard drives are pretty cheap, so if it is on its way out, its not worth replacing the computer over. If you want more performance, you may be able to upgrade the GPu without causing a bottleneck, depending on what I5 and GPU you have.