If it were mine, I would not even consider sending it anywhere to put some screws back in, but I'm not you, and cannot say that it is within your abilities.
That being said, why not just carefully take the rear cover off. And see if you can put the screws back in?
Also, someone else here may be able to assist you in determining the specs on the screws so that you can obtain a replacement screw for the one that's missing.