Convicted means found guilty of a crime. You can be found guilty by trial, or by pleading guilty or no contest. To answer your specific questions:
1) Are you going to be convicted? There is no way to tell without knowing the facts of your case, reviewing the police reports, interviewing witnesses, viewing evidence and conducting an investigation.
2) Convicted means to be found guilty.
3) Since you are charged with a felony, your should plead "not guilty" at your first court appearance. If you do not have money to hire an attorney, ask the judge to appoint the public defender.
Guilty and no contest pleas are pretty much the same thing. If you enter either plea, the judge will find you guilty. "No contest" just means you aren't admitting you committed the crime, but you aren't going to fight the charges. Years ago, a "no contest" plea couldn't be used against you in a civil suit, if somebody sued you based on the same facts as your criminal case. In California, a no contest plea can now be used in a civil suit if the offense is punishable as a felony... and grant theft is.
4) Again, there isn't enough information to know. If the charges are dismissed or you are found not guilty, then you aren't going to jail. If you are convicted, you might.
Now, a few notes on employment applications. Generally, an employer can't ask about any arrest that did not result in a conviction. However, a potential employer CAN ask about an arrest if you are out on bail pending trial, which describes your current situation. See California Labor Code §432.7.
I agree with the assesssments of my colleague, who has addressed all of the salient points pertaining to your question. In addition to his comments on point 2, a conviction is final upon sentencing. At the stage of proceedings where you are, you are about as far away from that point as you can be once these proceedings have been initiated with you being charged. I also urge you to at least discuss this with an experienced criminal defense lawyer admitted to practice law in CA as soon as possible. A number of excellent lawyers list here on Avvo.com who are licensed to practice law in CA. Check out their listings and call a few for a consultation. Until you do, you should not be making any decisions about how to resolve this matter. Good luck.
This response does not constitute legal advice. Given the nature of this website, it does not create an attorney-client relationship. This answer is provided solely for informational purposes, for you to use as a starting point when speaking directly with a lawyer in your State. I urge you to immediately contact an experienced criminal defense lawyer admitted to practice law in your State before you make any decisions about this case.
Grand theft can be charged as either a felony or a misdemeanor. It's up to the prosecutor's office how to file the case, but even if a felony is filed, it may be able to be reduced by the judge.
Theft charges can have lasting effects on a person far beyond just a conviction and any punishment. The issue you raise - job applications - is one of the biggest burdens to a criminal conviction.
Most of your other points have been addressed, but I'll offer this one piece of advice: Don't go this alone. You don't mention where this case is pending, but a consultation with a criminal defense attorney in the jurisdiction where this is going to court isn't a bad idea. There may be things an attorney can do to keep this from becoming a conviction in the first place. Every case is unique, but you'll never know what your options are until you discuss it with an attorney. Mr. Marshall is in Chico if you're in his area. I'm in Orange County. Feel free to contact either one of us if we're local to your case.