You must be new here - welcome!
Your first step should be to look through old posts - there is a wealth of information on this forum, infinitely more than you could possibly hope to extract from replies to your thread.
That being said, you should know that AMCAS does not combine graduate and undergraduate GPA's; when you apply to medical school, your your cGPA, sGPA, and gGPA are all looked at as separate entities.
Your stats are good, and your situation of having to work full-time will be understood by admissions committees, in my opinion. Yes, your first priority should be a solid showing on the MCAT; combined with your current GPA, your numbers shouldn't hold you back from getting at least one acceptance, provided the rest of your application is solid.
If you have the time and resources to do an informal post-bac to make your GPA even more competitive, then I think that is a good idea. I would strongly advise against doing a Masters; if you want to do research that badly, there are much cheaper ways to do so.
Best of luck.