If you want to save money and time (and don't care to lose info inside the phone, like pics, etc perhaps because you have backed up everything important) you can probably just do a factory reset. It is really easy to do from the menus. If you no longer can get to the menus, then you can do it by pressing two keys at the same time for certain time. The specific details depend on your phone model (often you press the power and the volume-down keys simultaneously for 30 secs or so). You can probably find it with google or in your users manual (which you can also find with google).
Factory reset means the phone will be like the first day you bought it. All data you have added since you bought it will be deleted, as well as apps you have installed, pics you have taken, etc.
Then again, you are supposed to back up anything important in your phone, if for no other reason, that you can lose the phone at any time (stolen, lost, irreparably damaged, etc) . Perhaps you already have (even accidentally by choosing the option that syncs everything with google, even if you didn't know you did).
Depending on what it is, a technician may have to do exactly the same. But perhaps s/he may be able to recover some of your data (if you din't back it up).
Good luck.